Super coupe bucks at boost what to do next?

BigTbirdcoupe

Registered User
I just purchased a 1990 sc and it is a little hard to start (I gotta crank for a few seconds. And when I accelerate it will go nowhere when into boost. I can't even floor it in neutral it'll turn 5500rpm with out boost but if I try to rev it by flooring it same thing happens I did spark plugs auto zone had to order wires, ran a koer and koeo with a scan tool all I'm getting in is (11ok) and (225 or 25 which Knock not sensed under accelerated test). I'm running back to parts store for fuel press tester cuz mine is lost, a blower belt bc mine is dry rotted and could be slipping and a cause bucking?. Also heard the cam sensor could be the culprit or egr, I couldn't locate the egr I'm not shure if this one has it or if it's been deleted altho the car is 100% stock with a little over 100k on the clock. Any tips are greatly appreciated I'm no dummy just new to the super coupe haven't really tinkered with many odb1 ford's Thanks alot for any help
 
Which plugs did you buy and what gap did you set them at? the spark could be blowing out if the gap is too wide.
 
Are you saying it bucked under boost before you did the plugs?

It did since I bought it b4 the plugs I tried plugs first bc my 300zx tt was blowing spark out of the stock plugs once I made some upgrades I did not gap them when I installed bc the auto part man said there pre gapped wrong!!! Afterward read the box stated to gap them. I will do this in the morning. I bought a fuel filter something I buy any way when buying a car, and got a new cam position sensor which a couple people told me. Car start rough sometimes but runs beautiful if I just cruise it I can run the interstate without making much over 2psi and it'll run up to 100 fine soon as u gun it blahhhhhh pinging. If I matt it in neutral it will also blahhhhhh ping sneez and almost wanna die but as soon as release throttle run great also kinda vibrates at idle not a miss but u can feel that to about 1100 rpm then super smooth kinda felt like a vehicle I had once with the wrong weight on a BBC 454 flywheel. I'm shure its simple on this t bird because it runs so great all the time when it's just idling and cruising
 
stock Motorcraft platinum from autozone it had autolight I believe coppers in it

Which plugs did you buy and what gap did you set them at? the spark could be blowing out if the gap is too wide.

All the tune shops around here use v power ngk in all the boosted cars around here race and street use domestic and foreign and for the t bird there half the price of the stock Motorcraft plug but had to order take 2 days so I got what they had anyone using these plugs or what is the best I plan on doing pulley, injectors, tune, head gaskets and so on but I want I'd to turn up stock first and work.the bugs out of it for awhile.
 
how about a dis or a air bypass

90 Auto SCs dont have EGR, no or erratic tach would indicate bad cam sensor
How about bad DIS or air bypass I've got a odb1 scan too that will show data stream such as air bypass voltage, o2,tps,rpm, and a couple other items will any of these readings determine if one of these parts are bad? I just don't know what the voltages are supposed to be everywhere I look it is hard to find any info on stuff like that.

How about the koer test which Said knock not found at accelerated test code 225 could a knock sensor be the issue I found some post saying don't worry about that code yadayada?
 
How about the koer test which Said knock not found at accelerated test code 225 could a knock sensor be the issue I found some post saying don't worry about that code yadayada?

Knock sensor (KS) not sensed during dynamic response test.
This code is generated when the "goose" test is performed during the KOER test and only means that knock was not detected during the test. Of course, there may not have been any knock to detect either. This code would have been generated during a previous KOER test and not cleared.

Clear the codes, be sure the engine is warmed up, run tests again, and when it says to goose it, give it the boot.

In the end, tho, I think you'll find the issue is related to spark plugs and/or wires. Be sure none of the plugs are cracked from being removed/installed. Be sure that all plug wires are fully seated...this is the hard part since there is so little room to work.

By the way, how did the old plugs look?
 
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the old plugs were pretty golden brown but real old not the worst I've seen

I did the test several times cleared the codes and retested all the same I am going to try to get the wires on it tommorow and re gap the plugs it wasn't really all that tight because I did away with the ac lines first. So how about the rest how much fuel pressure should it have at idle I was told 36psi and around 45-50 in full boost but it won't turn up hard enough to build full boost only about 3000 rpm and 5-7 psi the gauge maybe off because it's under 0 at about when the car is off it runs about -25 -28 hg at idle but I have other gauges to properly test boost when doing fuel pressure test. So I should return cam position sensor and are the factory Motorcraft plugs good and what should I gap them I know what the car says but I also know everyone has there sweet spot for there setup too. Thanks for the replys so far I'm shure its something simple as soon as it's solved I'll share the news unlike alot of people who use advice and run because that how it seems when looking up old threads on this subject. That's why I keep throwing diffrent parts out there because that's what Is in other threads but they just end and know one tells how the car was fixed kinda like a crap pyramid story book lol
 
Those are the correct fuel pressures.

Are you sure it's running premium fuel?

25+ inches of vacuum at idle?

I'd install the new cam sensor...consider it a tune-up part. Same with O2 sensors.

.054 (.052 ~ .056) is the stock gap for stock dual platinum plugs.

Check the firing order (some of the books have it wrong):
PlugandWireLayout.jpg
 
Yeah almost to 30 at idle with stock guage

Those are the correct fuel pressures.

Are you sure it's running premium fuel?

25+ inches of vacuum at idle?

I'd install the new cam sensor...consider it a tune-up part. Same with O2 sensors.

.054 (.052 ~ .056) is the stock gap for stock dual platinum plugs.

Check the firing order (some of the books have it wrong):
PlugandWireLayout.jpg
Yes -25+ hg at idle on stock guage it is also not a 0 when engine is off its about-5 to -8hg so that puts me around -17 to -20 ish when running is that decent good or bad what should a healthy one of these engines pull with no vacuum leakes?
Thanks alot for that ill use it.Well not shure about the gas that's in it got it from a old man that cruised it on weekends so I'm gonna fill with some premo tommorow to along with everything else that comes in

My girlfriends 2001 3.8 mustang kinda did the same thing at hard acceleration above 4500rpm never through any codes every part checked out great with a multimeter changed plugs wires egr sensor then had a guy tell me the coil pack on the distributer less ford's have tendency to act up like that I changed it been runnin like a raped date since. Do you think it could be putting out enough to run under normal conditions but when cumbustion chamber pressures rise the spark cannot travel or is blown out? I just don't wanna keep throwing parts at it tommorow I'll
 
Ah, yes, the gauge is wrong then, and 17" at idle in neutral would be close enough/good.

Confirm the gap is correct and eliminate spark as a suspect.

Could also be plugged cats....bad grounds (low volts), trashed wiring, water in the fuel, blocked air/fuel filters, slipping belts. Do you know how to check the fluid level in the supercharger? Be careful removing the fill plug...there can be residual pressure and that stuff stinks.
 
battery is new red top optima

Ah, yes, the gauge is wrong then, and 17" at idle in neutral would be close enough/good.

Confirm the gap is correct and eliminate spark as a suspect.

Could also be plugged cats....bad grounds (low volts), trashed wiring, water in the fuel, blocked air/fuel filters, slipping belts. Do you know how to check the fluid level in the supercharger? Be careful removing the fill plug...there can be residual pressure and that stuff stinks.

Has new battery, ordered a new sc belt mine is cracked a dry rotted
New airfilter, don't know how 2 check sc oil, and is it gear oil? Also bought new fuel filter just no time to install today. Getting plug wires tommorow too. Coil pack? Or Idle air bypass i found on a site says about the same symptoms. It never dies just runs like poop 1/4 throttle or more in boost. I will try some more tommorow and let know what I come up with. Seems to have good flow out the exhaust and it doesn't stink like it's burning the cats they will get punched out eventually tho just to let her breathe
 
See this thread about supercharger oil & fill, etc. http://www.sccoa.com/forums/showthr...il-change-question&highlight=supercharger+oil

If it were coil pack and/or IAC, I'd usually want to see codes for them first - a bad/failing coil without codes might be involved in your current issues...would be nice to have a known good one to swap in to test. IAC would be more of a suspect in starting/idle issues, and usually honks like a goose if it's ruptured. But they do age and don't cost that much to replace, I think.

Right now it needs the plugs checked again and new plug wires, so I'd focus on getting those done first, then see how it runs.
 
My experience with collapse on boost was the DIS.

Car ran fine as long as it stayed out of boost.

On a full throttle run it would cut out at 7lbs of boost and literally throw you into the windshield it quit so quickly.

Paul
 
thanks KMT plugs are gapped about tight 52

See this thread about supercharger oil & fill, etc. http://www.sccoa.com/forums/showthr...il-change-question&highlight=supercharger+oil

If it were coil pack and/or IAC, I'd usually want to see codes for them first - a bad/failing coil without codes might be involved in your current issues...would be nice to have a known good one to swap in to test. IAC would be more of a suspect in starting/idle issues, and usually honks like a goose if it's ruptured. But they do age and don't cost that much to replace, I think.

Right now it needs the plugs checked again and new plug wires, so I'd focus on getting those done first, then see how it runs.

Yeah and Tha auto zone gave me paperwork for primary and secondary readings on the coil. Are there test procedure with a multimeter I can test dis and iac lime a thread with certain readings? Waiting for the auto store to call got wires and a supercharger belt coming in today I'll spread the news as soon a I get it back together
 
DIS/Coil see:

http://mnharms.com/tutorials/disnostart/

...and for an overview:

http://www.dainst.com/info/edis/edis.html

IAC:

FORD IDLE AIR BYPASS

Ford doesn't use idle air bypass to regulate idle speed on its older throttle body (CFI) applications, but uses a solenoid or vacuum diaphragm instead to open the throttle linkage. Idle air bypass is used only on multipoint injection applications. On older pre-OBD II cars, codes 12, 13, 16, 17 & 19 all indicate idle speed is out of spec (too high or too low). Codes 47 and 48 indicate a fuel mixture problem which could be caused by an air leak. On OBD II vehicles (1996 & newer), codes P505 to P509 indicate a fault with the idle speed control system.

The diagnostic procedure when any of these codes are found is to turn the engine off, unplug the ISC bypass air solenoid connector, then restart the engine to see if the idle rpm drops (it should if the ISC solenoid is working). No change would indicate a problem in the motor or wiring.

The ISC solenoid can be checked by measuring its resistance. With the positive lead of a digital volt/ohm meter on the VPWR pin and the negative lead on the ISC pin, measure the resistance of the solenoid. On many applications, the spec calls for 7.0 to 13.0 ohms. If it is out of specs, the ISC solenoid is bad. Also check for shorts between both ISC solenoid terminals and the case.

If the ISC checks out okay, check for battery voltage between the ISC connector terminals while the key is on. Voltage should also vary when the engine is running. No voltage indicates a wiring or computer problem.

Suggest you pick up an EVTM off eBay if you like checking wiring, etc.
 
99% of the time bucking is caused by ignition problems which are usually plugs or wires. Sounds to me like you have a bad plug wire which is not uncommon.

David
 
coil tested!

99% of the time bucking is caused by ignition problems which are usually plugs or wires. Sounds to me like you have a bad plug wire which is not uncommon.

David

I tested coil pack from a bulletin from auto zone says primary is supposed to be .3 - .9ohm mine all test high starting at about 1.5 and the longer I hold it will come to about 1.0- 1.1ohm that to.much resistance right . Secondary tested 12.5 kohm and spec sheet says between 10.5 - 16.5 kohm so that's in spec. Leaving right now for fuel, wires and sc belt. should i grab a coil with these primary readings? Also it looks original ford logo and part number and real rusty at Mounting plate. And the little resistor is a bit corroded I'll clean all connections when I reinstall
 
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