Help! car stalls as soon as it gets boost.

8

84ttype

Member
Joined
Dec 24, 2004
Mods are in my signature, heres the story. I had the motor freshened and swapped to a roller cam (thats not in my sig yet sorry). car was running great put about 150 miles on it. couple short runs easing it up to 4~5 lbs of boost no problem. heres where it starts... car was down to about 1/8th tank went to the gas station filled it up, felt it was running good so i ran it up to about 9 lbs of boost this time, no problem at all... about a half mile later though it throws out code 44 exhaust rich. pulled over left it running checked for vacuum/exhaust leaks fluid leaks , anything basically. everything looks fine, went to get in the car and the check engine light was already off so I put about another 50 miles on the car NO boost just cruising on the freeway and the scanmaster erased the code 44 so went home and put the car away... next day (I should emphasize that I did NOT mess or fiddle with anything on the car!) tried to get on the freeway and as soon as the car went into boost it stalled and the check engine light came on briefly and then went off. tried a couple more times same result, If i push the gas too hard it actually backfires through the intake. watched the fuel pressure and noticed it wasnt going above 40lbs. parked the car adjusted the fps to 43 line off(it was around 38lbs before) tried again and it still stalls but what happens is as soon as it hits boost, engine stalls fuel pressure shoots from 40lbs to 45lbs the check engine light comes on and then it backfires if I dont let off the gas. I pulled the fuel pump (Its a denso Supra pump I threw in when Walbro was having their "issues") and the sock is brownish yellow but not collapsed. couldnt see anything in or around the pump. I'm taking a shot in the dark guessing the pump "ate something" but Would it still work fine under vacuum?? and should I be checking anything else? I'm lost at this point.

also car hasnt thrown code 44 since so that may not be related
 
before I threw a pump at the car, I threw a new vacuum line from the compressor to the FPR. problem solve must have been blowing by one of the ends under pressure...

I am an idiot... end thread.
 
Update: so the same problem has returned after a couple weeks... this time I replaced the hoses to the fpr the wastegate and the map sensor then I plugged the vacuum block completely (no vacuum lines now) and it just made the problem worse! I can't even get 1lb. Of boost before it cuts out and backfires through the intake.
 
turn regulator screw in while running...all the way in you should be able to get 100 psi....if not, you have a delivery problem....
 
I went out and tried the fpr. It goes to to 100 psi no problem. I also checked the resistance on the coils and they're at 11.8 11.8 and 11.2 ohms. plugs are delco 42ts gapped at .32 the ends are a light tan color but some have oil on them?! I pulled them all and each one has a little residue but the number 4 plug was soaked in oil!!!!
 
Pull the valve covers and take a look. I had the same problem a while back. I had one of the plastic buttons that hold the rockers onto the shaft break off. Rocker would move around, ran fine sometimes but almost always trying to build any boost it would do exactly what your car is doing.
 
On the FP; Verify the “T” on the back of the manifold below the turbo. It feeds the FPR and the MAP.
On the oil soaked plug/cylinder . . . Run a compression test and post back.
 
I have my fpr tee'd off if the wastegate line that comes out of the compressor. But I switched it back and tee'd off the Map sensor line with no change in symptoms. All of these lines are brand new. I also hooked my air compressor up to the fpr directly with 20 lbs in the line and the gauge shot to 60lbs. So I know for sure it's not a fueling issue at this point. I'll have to wait til tommorow to borrow the gauge from work for the compression test.
 
oil will cause detonation and timing retard.............and backfire from plug blowing out...........
 
Take the doghouse off, and see what is in the #4 runner. The gasket may be leaking and pulling oil into that cyl.
 
84ttype said:
I have my fpr tee'd off if the wastegate line that comes out of the compressor. But I switched it back and tee'd off the Map sensor line with no change in symptoms. All of these lines are brand new. I also hooked my air compressor up to the fpr directly with 20 lbs in the line and the gauge shot to 60lbs. So I know for sure it's not a fueling issue at this point. I'll have to wait til tommorow to borrow the gauge from work for the compression test.
Click to expand...
Good test! Sounds like there is no problem getting the FP up.
You appear to be very capable . . . .
Are you 100% sure it is oil and not gas?
It sounds to me like the car is running too rich. . . . . try it with the alky off.

As stated earlier . . . .
If there is oil in the #4 cylinder, it needs to be resolved first and foremost.
After that . . . . my suggestion is to get some type of recording scantool . . . and post a log.
 
Yes its still a hot-air car.

didnt have a chance to hook up the powerlogger yet. but compression is around 140 on all cylinders. plugs look a little fouled like its running rich now, but none were soaked like last time... sorry guys i have two jobs right now but I'm working on this whenever I get a chance. I'll try to get it out tonight with the PL hooked up.
 
Thanks for the advice Chuck but I've gone waaaayyyy past the point of no return with this setup, lol.

So it gets stranger, I hooked up the Power logger and took the car out for a test run... and its running fine now?!?! The only I touched since the last drive were the plugs and wires to check compression, but the problems seems to be gone again. I cant imagine a loose plug or wire would cause it to do that, it was idling and cruising fine. could this be a coilpack, cam or crank sensor issue?

Heres the log from tonight. I had it running for the whole trip but if you skip to the end I had a good pull up to about 9 lbs of boost. dont be alarmed by the air temperature. my sensor is plugged straight into the intake manifold.
 

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About another 100 miles on the car. hasnt had that same problem again yet... although it did just throw a code 45 today for the exhaust being too rich now... changed the plugs after the compression test above so I'll pull them tommorow and see what they look like, might replace the o2 sensor just to be safe (current one is about 3 years old.). If the issue doesnt show again I dont know what say other than I guess it was a loose plug or wire, although I still dont understand how that would only affect the car under boost.
 
Mine is stock. Engine rebuild last Sept: 212/212 cam, 38lb injectors. Nothing fancy at all. Recently was getting code 45. Engine would stall and shut down on fast deceleration. Found leak at EGR, blocked off EGR but didn't redo pressure check so was getting same code again. Just get it back from the shop: resealed that block off plate, plugs/wires changed, oil changed, MAF sensor replaced with new one, IAC replaced with new, original MAF hose with small leak tapped up for now until cold air kit set up, fuel pressure regulator replaced with new adjustable one, electrical ground check-replaced neg battery post. NOW no engine light on so far, nor code 45, but BL continues 105 just like before the above maintenance. Car has not stalled or shut off. TPS was adjusted to .38 where I had it at .42. (Side note: rear brakes adjusted, passenger side valve cover breather placed and turbo bell bypass capped, throttle body cleaned. I've also noticed slight buckling at hood rod/shock bracket site, this after replacing the old worn out set.)
 
Thanks for hijacking my thread.. just kidding don't worry about. Whats your fuel pressure at? They always say start with the easy stuff, I'd turn it down a couple pounds and see if that helps. As long as there's no KR your alright.
 
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