My Hot Start Sega.. (updated)

91 XR7

Registered User
Well my Hot start issue is still there, only needed to run the car for like 15-20 minutes, wait @ the same amount of time and it was hard to start and when it did it idle at like 400-500rpms very roughly and with like 1-2 inches of vacuum running EXTREMELY rich, with a mild smoke screen filling the back yard. It was running like that for nearly 5 minutes and it didn't change.. nor did the Check engine light even turn on?? You think idling at 400-500rpms, rich as sin would set off warning bells inside the ECU :rolleyes:

Things replaced/tried:
  • Spark plugs
  • Spark plug wires
  • Fuel Filter
  • Positive Crankcase Ventilation Valve
  • Air Filter
  • Dis module
  • ECT sensor
  • Coil Pack (from a good running car with no issues at all)
  • Cam sensor
  • Crank Sensor
  • Idle Air controller (From TWO different cars that have no issues)
  • Throttle position Sensor (As above)
  • Injectors removed, `sonic cleaned', Checked for leaks, ectra
  • All Inter cooler tubing resealed twice
  • Inter cooler Replaced on second Tube resealing (had it sitting around, and i removed everything to make sure i had CLEAN surfaces)
  • Return Plenum checked
  • Grounds checked, and 4ga even added (Battery to chassis, Battery to Engine, Engine to chassis)

Only things not messed with/checked yet are:
  • Mass Air Flow sensor (does this same thing unplugged?)
  • Intake Air Temperature sensor
  • Barometric Air pressure sensor
  • Oxygen Sensors (how can it be them on start up?)

Now at this latest time, instead of blipping the throttle which always gets it to run `normally', i got out an Allen key and slowly opened up the Idle air bypass screw after like 2-3 turns out, it caught and started to run `normally' again.. after the car had a chance to clear itself with a few WOT throttle hits at the throttle body i shut it off, came back like 10 minutes later and it was easier to start (had a hint of not wanting to thou)

If any one can help me on this it would be awesome.

Previous threads on this same problems
Issue Link one
Link Two
 
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you ever ruled out the fuel pressure regulator??

disconnect the battery for ~30 min to clear adaptive memory
remove and cap off the fuel pressure regulator vac line

stand by with a fire extinguisher just in case it spews out some fuel
 
Sure sounds like the injectors are leaking to me....

He said they were cleaned and checked.

Have you checked MAF and TPS voltages? You say the IAC was replaced from 2 different cars. It sounds like you are putting used parts on the car to try to remedy the situation?
 
Decipha, DLF

Regarding the FPR:

Before I installed the serviced injectors into the intake manifold, I did power up the car, turned the key to the `run’ position and grounded the Tan W/ Green tracer wire at the Self test connector, and ran the fuel pump for around 2 or so minutes as is.. None of the 6 injectors leaked during that time, nor did the FPR.
After everything was installed, and I was still having these issues with the 2nd set of injectors I install (the serviced ones above, issue was there with the Originals) I checked the FP with and without the Vacuum line attached (at the inlet Plenum) which where all within spec, and no fuel was coming out the vacuum line to the FPR.. Also the ability for the system to hold pressure was good (going by my shop manual) and built right back up instantly when I turn the key. Even when the pressure was relieved, the Fuel pressure went to ¾ of where it should have been as soon as the key was turn to the run position and was at the correct pressure after a the first revolution or so of the engine being turned over..

Regarding the Injectors:

The set of injectors in the car are not the Originals, but have been serviced/Cleaned by professionals, and leak tested, ect. Even before I set them into the intake manifold, I ran the fuel pump for least 2 or more minutes without a sign of a drip from them or the FPR..
This issue was also there with the original Injectors that were in the car (I had a spare set serviced/cleaned) and these were installed for the exact same reason that is suggested to me many times, that the ones in the car were leaking, causing a flooding/flooded situation on started up.. Can the injectors go bad (leak) only after they are installed?


Sorry for the long winded posts.. but i believe the more information there is on a issue the better it should be to figure out what's causing the issue :)
 
OK, If it's not the injectors, then something else is telling the PCM that it's lean, and to add too much fuel.

Have you swapped out the MAF with a known good unit?
 
Have you checked MAF and TPS voltages? You say the IAC was replaced from 2 different cars. It sounds like you are putting used parts on the car to try to remedy the situation?

There's one thing i forget to mention thou.. i have checked the TPS voltages from Idle position to WOT and it was good..
The MAF, other then cleaning it Carefully (like i've done many times on my other 3 MN12's (one dating back since '97), i have no clue as to how to check it.. to see if it is sending the correct voltage at that time and moment.. I also keep reading on here and TCCoA, that if you unplug it that the EEC will revert to a set values.. but even unplugged it does the same thing?? (honestly i'll have to recheck my old threads since my old age is getting to me :(

Well the IAC is used.. One i borrowed it from my '91 XR7 which has NEVER gave me issues on it (heck was able to start it the other weekend after sitting since last summer, the Throttle blade stuck abit but the car started, fast idled, and came down to it's normal idle.. the other i borrowed from my '89 XR7, it too has never had an starting or idle issue..

I do have a IAC tester/controller. I can get the Idle speed on the SC down enough so it can just run, in turn simulating a bad IAC or IAC circuit but it doesn't do the smoking thing.. (which is dark and smells of unburnt fuel)
 
Have you swapped out the MAF with a known good unit?

the only spare i have for a 3.8SC motor is the one in my '89 XR7, which is the 55MM version, and my '91 SC has a 70? MM version.. so i don't know if they are compatible?? Or can i just swap sensor themselves (doughtful)

If one from a '92 SC will work, i have a friend who has one that he's not driving (the car is kept in a semi heated Garage)and ask to borrow his??
 
I did a search, and found this:

Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue)
 
I did i mild search myself after my post.. But didn't find anything about voltages? all of them of varying numbers from .4 volts to .6 volts..

My Manual, for 1992 T-birds/Cougars says a signal of like .36 to 1.5 Volts :confused:

Since it's on CD i know i had other specs on it but can't find it :( But .6 Volts at idle seems about right thou.. But since it's not at the `right' idle at that time......

Like to test my BAP sensor too, how to do that? Probe the Signal wire and ground or signal wire and positive? My Multimeter does do frequency so.. The car is near sea level, in turn meaning it should be producing a Frequency of around 159hz..
 
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Also is there a way that the Reference voltage change between KOEO and KOER? IE from a bad voltage regulator??

I'm just wondering if at KOEO that the EEC checks the voltage and all si good, when the key is turned to the start position something happens, the voltage spikes to whatever, say 12 volts, and is now sending 12volts to the BAP and TPS, making the EEC thinking that the throttle is at WOT, so causing it to add more fuel then the air entering....

But that should in theory still cause a CEL though right??
 
The only thing that I see that you may be missing is the IAT sensor. It along with the MAF and ECT and of course HEGO sensors. If it is indicating the wrong voltage it can cause a rich condition during cold start. Much like the ECT can. I would check that out.
 
When Cold, sitting over night for like 10+ hours, it starts Perfectly, it's only when it warms up does it have issues... and only if you let it sit for like @ 10 minutes
 
My 89 SC was doing this last fall. I replaced the Coolant Temperature Sensor thinking that would help, but I parked it before I could really tell if it helped. Just thought I'd throw that out there if you hadn't tried that.
 
This weekends leg of this Saga

Well i went through all the wiring today, all but one ground (the one next to the EEC) were good, with the one only be slightly corroded. I totally forgot to bring back my BAP sensors, which i removed to test outside of the car in which i didn't do.

i started the car up as-is and when it started up it idled around 1300RPMs for a little (had to be 15+ seconds) before settling down to around 900rpms (This is with the Air bypass screw open like 2-3 turns which i was trying out something last weekend?) Only until i turn back in the by-pass screw to around 1/2 turn out did it start to idle @750rpm.. the last time i ran the car it idled at @750rpm with the bypass screw opened that much (@600-650ish with the IAC unplugged)

Oh and i got a Keep alive error code, don't know if that was from the last time i ran the car, or this time when i disconnected some of the connectors, removed grounds to clean them before starting it today.. but would the car run if no power is going to pin 1???
 
If there is no power to the EEC, then you won't have any KAM codes from previously, so that code has come up since.

Pin 1 is the main power to the EEC.

If you are having to turn in the bypass like that to bring the idle down, I say you have a vacuum leak.

Fraser
 
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