Warm start Idle issue

91 XR7

Registered User
Did a quick search, found a thread 4 years old with some good things to look at.. looking for more up to date thoughts?

Dealing with a '91 SC 5spd (172K Kms on it)
Cold it starts up great, and but recently warm starts ups have been an issue, specially the longer the drive..
When you start it, it runs rough, idle up and down, with the Vacuum gauge at @10inches of Vacuum.. Usually a couple `blips' of the throttle gets to idle decently.. even left alone it will settle to a nice idle with like 20 inches of vacuum with in 10-20 seconds. (haven't timed it really)
The most recent thou (Say around 50 miles highway driving, 10 miles city) after having dinner (30-40 minutes) it was the worse so far, and swore it was going to stall out too..

I may try seeing if anything is under the DIS module or not.. even thou all previous work was done by a Ford dealership, but that doesn't mean much there :p

Fun car to drive thou, even thou the 2.73s have got to give way to like 3.27s :p
 
First check the base idle with the IAC unplugged. Start the car and see at what rpm the engine will idle on it's own...you may need to coax the throttle gently to keep it from stalling before it will settle - it should eventually idle on it's own, but at a reduced rpm (if it idles fast, there may be other issues to be corrected before proceeding). Twist the idle stop screw on the linkage (to crack open the throttle plate) 1/4 ~ 1/2 turn at a time until it cooperates. No more than one full turn at this time.

Reconnect the IAC and re-check warm idle.

If the car still has the same symptoms, continue to up the base idle...turn the idle screw on the throttle plate stop a full turn and see what happens.
 
I would not mechanically adjust the idle or throttle blade. A hunting idle is a classic symptom of too much fuel which also coordinates with your good cold starts but bad hot starts. When cold the IAC is allowing lots of air into the motor and it needs more fuel anyway. When it's hot the IAC will be mostly closed and the motor won't want near as much fuel.

Check fuel pressure. It should be about 32psi with the motor idling, 39psi with the vacuum line removed from the regulator, and should rise above 39psi pound for pound with boost when driving. Pressure should hold for awhile after you shut the key off.

Clean your throttle body. They can get gummed up which may prevent the expected amount of air to bypass the throttle blade. If this is happening the motor will essentially be "choked" when warm. The fact that it clears up after 20-30 seconds is most likely a function of adaptive control taking over to correct the rich condition.

Check your ECT sensor. If the EEC thinks the motor is cold on startup but actually it is not, the strategy will be all off and again, be adding too much fuel. Low coolant levels can also cause this problem because air pockets tend to form near the ECT sensor preventing it from reading correctly. Low coolant and a misfire on hot restart are also symptoms of a leaking headgasket but hopefully that is not the case here.
 
well i think the idle air bleed screw is turned out some, since i have played with it abit before? since it would just idle (@500rpm)when warm with the IAC unplugged and stall out if you turn the screw in abit (1/2 turn??) (sorry this was last year after i got the car, but it's only since insuring it this year this problem started?? :confused: but know back then if you plug in the IAC it'll go up to it's "normal" idle of like @800rpms

Also with the fact the idle Vacuum being at like 10 inches i think the IAC is doing its job (along with the EEC) to try and get the Idle how it's suppose to be when it acts up like this.. (when idling `smooth' (has a slight roughness too it) it's a solid 20 inches day in and day out)

Dave, what you say about Adaptive sounds nearly right too.. Since typically O2 will take like 15 seconds or so to Warm up and be good enough to use for reference, which is about when it starts to clear up.. So it Adapting itself to a rich mixture is very possible.

I just have a feeling it may be injector related? since when i got it the Fuel filter was collapsing from all the dirt it had in it :eek: I know i have another 12 30# injectors i can send out to be cleaned, and flow checked

Maybe i'll see about swaping over the FP gauge from my '91 XR7 (just a little 1" VDO) to see what kinda FP is at the rail

Also i wish i had a known good ECT, but i don't (the one in my '89 XR7 questionable, Since the cooling fan turns on on COLD start up for like 10-15 seconds, could be something else thou) Could be a good thing to replace thou.. it is a 18 year old sensor swimming in antifreeze..

and i'm fearing having to do head gaskets right now :eek: mostly don't really have the time to do it :)
 
>I would not mechanically adjust the idle or throttle blade. [/I]

I wouldn't either, normally, except that these cars are long enough in the tooth that there can be wear at the point where the idle stop screw hits the body/stop. This should at least be checked on high mileage components.

> A hunting idle is a classic symptom of too much fuel which also coordinates with your good cold starts but bad hot starts.

>Clean your throttle body. They can get gummed up which may prevent the expected amount of air to bypass the throttle blade. If this is happening the motor will essentially be "choked" when warm.

Precisely - the throttle plate may not be bypassing enough air and that gap could need to be restored.

Not checking this as a base line may lead to tail chasing, so this is just a word to the wise to get this out of the way before going too far in other directions :)

ECT sensors don't normally fail, but I have seen them operate out of range. I took one out of service that was erroneously telling the computer the engine temp was 40 deg. higher than actual. Put it on a recording data meter and tracked it for hours...replaced it and fuel mileage increased 10%.
 
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ECT sensors don't normally fail, but I have seen them operate out of range. I tracked it for hours...replaced it and fuel mileage increased 10%.

Well i personally wasn't thinking it completely failed, other then maybe the one in my '89, But just not accurate anymore being that it's 18 years old with like 110,000 miles on it..

I will try to clean the body opening with some cleaner and a rag this coming weekend.. Honestly i know i had the tube off when doing the plugs and wires and can't remember how it look inside.. or if i looked :eek:

Also After popping the hood this morning.. it reminded me, it has an `aftermarket' DIS module.. So maybe maybe not it? And i do have a good, so i think, OEM DIS module i can try if need be..

I know when i messed with the Idle air By-pass screw i set it too like 200 or so RPMs less then if the IAC was plugged in, so it itself is not set to the `correct' idle speed.. i have never touched, and may never touch, the Throttle `blade' stop screw..
 
Check fuel pressure. It should be about 32psi with the motor idling, 39psi with the vacuum line removed from the regulator, and should rise above 39psi pound for pound with boost when driving. Pressure should hold for awhile after you shut the key off.

ok i really dont mean to hi-jack but ive got a question.

i have a fuel gauge on the rail and at idle it shows 39 psi. i have a 255 FI pump and 50# injectors and the stock FPR. and pressure drops immediately after shutting the car off.

what would cause a high reading like that ?
 
>i have never touched, and may never touch, the Throttle `blade' stop screw..

Not all SCs have the air bypass screw like yours - in that case, I believe you're right to focus on it.

Just keep in mind that worn components, such as throttle plate pivots etc. can leak more/less than they did when new.

Good luck w/your issues and let us know how it works out, thanks.
 
20 days later.. and sadly i haven't had the chance to check FP or anything.. Also been trying to find a FP gauge i could place on the hood/cowl and go for a spin to see what kinda Pressures i get..

BUT on the other side, i tried Seafoam, 1/3 in the tank, 1/3 through the boost gauge Vacuum fitting.. :) Bah.. After letting it stall, and sit for nearly 2 hours or more.. on leaving, only a small little cloud of smoke :(
Still have another 1/3 to go.. which i may add to the oil in the next week or so when i do the oil change..

Well the car now has a odd small `hickup' at idle untill it warms up some.. (after say 10-15 minutes of driving) after that i have never felt it/notice it again.. even in rush hour type traffic...
also added 200 miles the other day on it, with out an issue either.. Don't know what kinda gas mileage but i know the previous tank i babied (Staying out of boost as much as possible, shifting @2000-2500rpm, and trying to keep the RPMS below 2000) and it got a hair over 16 MPG
 
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After months of waiting.. was able to borrow a Snap on digital fuel pressure gauge.. and was able to find out what the FP is...

40 psi KOEO and 31 psi KOER

Also now the problem is getting worse.. On cool mornings it usually starts fine but it seems as the Ambient temps increase it takes more to start.. and it's more consistent in the hard start issue..

I noticed that a few times, just like above, when it does start but idles ROUGH around 500 RPMS when it finally catched (IE revs to like 1700rpms) or if you `manually' make it rev up (IE put your foot on the throttle pedal) there's a nice stench of unburnt fuel along with a slight blackish smoke out the tail pipes..

Fuel injectors have been replaced (serviced used ones that hold fuel, checked before reinstalling into car) DIS module been replaced (Good used).. Newer Crank sensor, Cam sensors, Plugs and wires, IAC looks newish too (checked it out when i had the SC off).. Coil pack i think may be original.. but on the primary side i was getting 0.6, 0.7 and 0.6 ohms of resistance..

Been talking to many different mechanics.. all say different things..
two say injectors, one said Coil pack, and another said the typical thing.. `Dis module'

And still has a `knock' like noise at times when driven hard for a second or less.. May be ping.. but it's not the typical `ping' i'm used to hearing
 
After months of waiting.. was able to borrow a Snap on digital fuel pressure gauge.. and was able to find out what the FP is...

40 psi KOEO and 31 psi KOER

you should monitor fuel pressure after key off. Take a measurement every 5 minutes and note it so you can see how fast fuel pressure drops off. The rail should hold pressure quite well.

That'll let you know if you have an issue with something leaking fuel into the manifold or intake ports.

Also if it's getting worse. Change your plugs and see if it gets better again, or at least back to the beginning. Your plugs may be getting fuel fouled.

Did you replace the ECT Sensor yet? Why not? If you are hesitant to spend the money and you have a digital voltage meter you could test it. You would need to stick the test leads onto the two wires going to the sensor and note the voltage as the engine idles. The voltage should change as the engine comes up to temp and the thermostat opens.

If the voltage doesn't change. Or the voltage appears to fluctuate rapidly, the sensor is bad.
 
Well other then having a leak at the fittings/adapters for the pressure sender.. it didn't seem too bad.. even after chatting for abit (say 15-20 minutes) well looking for the fittings/adapters when we hooked it up (with a little fuel spray during two of installs (first time one of the fittings leaked it was quickly removed, tightened, then installed again) and it still showed over 21-22 PSI.. But with still another leak in the fittings/adapters it did slowly drop..

Like i said, it is getting worse, initially it only did it after a long drive and it sat for awhile.. now it does it on a typical start up even cold.. (IE sat for 9 hours) So it's something that seems to be failing, it's just a question of when and what..

Also in the morning (@16degrees C or @ 60F) it's good.. but when it warms up in the day (Say mid 70's) it starts to have issues, like i said even after sitting outside of work for 9 hours.. (which should be enough to being it down to Abient temperature from the whole 5-8 minute/28 block drive to work) Also in the morning the ECT is showing around 2.2volts? and at work it's @ 1.7Volts?? (sorry forget the Values really :( But it's usually a smooth decrease in voltage as it warms up and i usually probe the one lead (not the grey/red) that goes back to the EEC and ground the other DVM lead to ground on the engine)

And i'll be getting a ECT and IAC from Ford this week (got to order them first) Since i can get them cheaper there then at a jobber store (Napa, ect)

Also i rather try and replace a known bad part then just start throwing things at it in hopes to fix it sooner or later... Might as while get a new car.. :p
 
2.2v is about 95F
1.7v is about 122f

What's your ambient temp in the morning?

you should use the other wire in the sensor. EEC ground is not necessarily the same as the ground point you touch on the block. Use the sensor ground for accuracy.

Have you done the EEC self tests for KOEO and KOER and passed?
 
like i said above.. morning Ambient temps are low 60's with Highs in the day approaching 80's..

I never drove today, nor do i have my test equipment with me.. (all at work) but i may drive again tomorrow.. And i'll be ordering the ECT and IAC (unless one from a '91 5.0L MN12 is the same?? )

I just wish i wasn't so busy.. But i'm hoping first thing in the morning i'll be calling up Ford to see about getting a IAC and ECT sensor.. I *MAY* also get a pair of O2 sensors..
 
like i said above.. morning Ambient temps are low 60's with Highs in the day approaching 80's..

I never drove today, nor do i have my test equipment with me.. (all at work) but i may drive again tomorrow.. And i'll be ordering the ECT and IAC (unless one from a '91 5.0L MN12 is the same?? )

I just wish i wasn't so busy.. But i'm hoping first thing in the morning i'll be calling up Ford to see about getting a IAC and ECT sensor.. I *MAY* also get a pair of O2 sensors..

www.rockauto.com has the motorcraft coolant temp sensor for under $30.00. the have a IAC (standard motor products) for $54. I have a rock auto discount code: 1628213418777 that expires on the 14th of June. put it in the how you heard about us field and save 5% off your total order.
 
Well As always i haven't been able to get to do the ECT sensor Since whenever i get a chance to work on my car it's after it's been driven for some time..

Was able to get a code, 117 ECT sensor is/was low or grounded , But i do not know if that was from my probing it or not since a couple of times when it was somewhat code i depending on how i probed it i was able to get the Cooling Fan to turn on :eek: But the last time i probed like how you, mike, said.. and got .42 volts at running temps..

But this week i did do the coil pack (back to the one in it) and the IAC.. and still does the same thing..

Today took a trip to work with the lady to drop things off at work since i'm not going to drive the car this week, and it started great with out a problem.. After going for a drive in a car at work for like 50-60 minutes get back in it, start the car and it ran at like @400rpms i just let it be 20 or more seconds later it still ran like that.. even told the GF `look at the smoke this car is making' then i said `screw this' and lightly pressed the gas pedal then as the RPMS started to raise that way it was like it finally caught and reved up to like 1400rpms, then settled down like normal.. with a big puff a smoke out the tail pipes.. Still smelt like unburnt gas with a twist of burnt oil..

Need a better description?? :p

But this week i'll try to get to the ECT and maybe even the TPS.. I'm also think now it may possible be Cam sensor?? Since it's, along with alot of other items, is covered with supercharger oil cuase the leaking nose cone seal (I need to rebuild the spare i have.. found them rebuilt for $500cdn exchanged thou :eek:)
 
Well tonight I replaced the ECT sensor, Cam sensor (used good one), Reinstalled the DIS module that came with the car, even the TPS sensor..

Before resetting the EEC, I pulled the codes and got 117 again..

Anyways.. tried to start it again.. This time even cold it didn't want to start untill a fair amount of turning over was done.. and didn't idle that good then either.. shut it off, tried starting it again same thing.. It may be the TPS sensor this time, but it seems to have a delay/stumble when you blip the throttle too...

Other then Crank sensor, which i thought the Up shift light would be lit up if it wasn't working when crank but it shuts off after the Second Compression stroke or so and never comes on again until i either let go of the key (car not started) or when it is "running"

Now i'm going to try getting a Fuel filter and see what that looks like again, Since the ORIGINAL one was pretty plugged up.. so to say the replacement hasn't been plugged up may be an understatement.. Since who knows what may also be in the gas tank..

I'm starting to think of parting out this thing.. which i originally thought of doing :( that and my '89 XR7
 
If you still get a 117 code (you cleared the codes before didn't you?), you need to track that down before worrying about much else. You'll need to back track the wiring to find where the wiring may be shorted to ground. This code means the voltage is too low, and with this sensor, low voltage means hot.

The hard start could simply be fuel fouled plugs from all the cranking you have been doing. If you had decent fuel pressure it's not likely that flow is causing a problem at idle.

If you changed your tps again, you need to re-verify the settings. Plus you need to pull the ground on the battery and let it sit there for 10 minutes or so to clear out the adaptive memory in the EEC-IV for your former combination.
 
I'll see about tracing back the wiring.. since this weekend (saturday to be exact) I cleared out that code.. and turning either that day or Sunday it came back..

when when i was working on it last night.. i had the EEC fused removed (Basically the same thing as disconnection the battery, but without having to reset the radio :p )

I can't see how the plugs can be fouled what at the beginning of cranking the car over, even during that time it seems like it's just not wanting to even try to start..

And also since i didn't bring home my DVM i couldn't check the voltage at the TPS..

I'm also thinking that since this problem is getting worse and worse, that sooner or later what ever is causing it to have a hard start issue will fail completely and i'll be able then to find out for sure what it is :)
 
Well boys and girls.. Driving around to day, for like a split second or less.. the car lost power..
but when leaving a shopping center this evening, and with it doing it's typical warm start issue.. as i was driving out of the parking lot, the CEL came on for like a few seconds then went off.. the first thing came to mind is DAMN! then suddenly i was think `YES i may be able to find out what the heck is wrong with this POS'

got home (ran good that whole drive) Pulled the codes.. and I got 212 and 214.. So differently an Ignition issue i have going on here..

Edit:
Well the car finally died, twice.. Got in it.. crank crank crank finally started but no Tach... Pull away from my parking spot (at the mall) it stalls.. then it was a battle to get it too start again.. got it to run for another 3-5 minutes, then the tach started again.. as soon as the tach started to get arratic, and die, the car just died.. tried to start it again well rolling (using the clutch) that didn't work... Anyways.. as it coasted to the side of the road, i gave up trying to start it.. luckly i had spare parts in the trunk and tools.. So with a hot engine I swaped out the cam sensor and DIS module, got in did the typical hard start issue but started and ran untill i got it to my storage place to pick up my '96..
 
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