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View Full Version : Engine misfire and backfire, need help



scbird1
06-18-2005, 07:23 PM
Im working on a 89 here and have run into a wall and can use some imput.
It starts but chugs and will barely stay running if you give it half throttle.
Here is what has been done thus far> Every sensor has been changed with known working ones including the coil,dis,computer, ignition switch,fuel pump relay,FPR. The car had about a qt. and a half extra oil, found out it was gas in the oil. Drained it out and replaced oil. its got to be getting good fuel. It has good spark on all plugs. Replaced the balancer,crank sensor= no change. Had the top half of the motor off to make shure all vacume lines and intakes were sealed. Car had even compression when checked. Took off the oil cap to make shure rockers were rocken, they were. No codes from scanner, gives me a {11 11} every time on KOEO and no stored codes. I pulled the wires off the maf , cam sensor, octane plug, spout connector nothing make a diffence.
Im just out of ideas unless it jumped timming but how can you tell untill you have the chain cover off? anyone have any ideas?

Max__Power
06-18-2005, 08:02 PM
The car had about a qt. and a half extra oil, found out it was gas in the oil. ?

How did gas get in the oil?

scbird1
06-18-2005, 10:36 PM
When a engine dose not burn the fuel it seeps past the rings and down into the pan. The injectors still work like the motors running even when cranking.

no164ford
06-19-2005, 11:24 AM
Dumb question, but did you change your plugs? I had some simmler problems turned out to be 2 filed plugs.

scbird1
06-19-2005, 11:35 AM
Wires and plugs have been changed. Nothing I have done changes the way it runs. Its as if its way out of time. I realy need some advice here. Im working on this for a fellow SCer who has yet to drive the legendary super coupe.

Phillio99
06-19-2005, 07:06 PM
When you replaced the computer was it with the right model year, or transmission? Could that be causing your problem? Maybe the car was destined to be a parts car!! Hopefully not,
Phil

scbird1
06-19-2005, 07:07 PM
Ok would anyone like to take a dumb guess? im just out of things to check for. Im down to 2 things here. ether its mechanical or possable wires grounding out. Hell im at a loss here

scbird1
06-19-2005, 07:42 PM
I swapped one in from a 92 5 speed and this is a 89 5 speed. It ran exactly the same but threw a bunch of codes. I put the right one back in. Just thought I would try anyway. I have herd that these engines will run without a cpu in limp mode but this one will still not run. It fires right up and dies ,backfireing and chugging.

David Neibert
06-19-2005, 07:47 PM
Ok would anyone like to take a dumb guess? im just out of things to check for. Im down to 2 things here. ether its mechanical or possable wires grounding out. Hell im at a loss here

Okay here's my guess...your getting way to much fuel and the cylinder walls are probably washed down. Check the fuel pressure...if it's not holding about 38-40 psi for at least 10 minutes after turning the key off (after cranking for about 10 seconds), then the diaphram is probably ruptured and allowing fuel to leak into the intake manifold from the vacuum/boost refrence hose that attaches to the top of the regulator.

David

Jason Wild
06-19-2005, 09:25 PM
I have two ideas that i have had come up on SC.
timming off a little the other is the wires are not in the right order on the injectors.

scbird1
06-21-2005, 01:01 AM
Well the FPR has been replaced and it holds pressure for more then 10 min.
Wires on fuel injectors on 89`s are marked so you can`t get them wrong but I checked the colors anyway. Ignition timming is controlled by the computer. Valve timming is set by the timming chain. This car went south and then was sold. So the new owner was told that the blower was shot. He put on a used blower and the car ran the same way. What would happen if a rag was left in the intake? Ok im reaching but have no where left to go but inside the motor.

Phillio99
06-21-2005, 01:35 AM
Hey I know we were talking about a possible bad ground. Could that be a source of the problem here? Wouldn't that cause intermittent problems? Just throwing stuff out too.
Phil

lube70
06-21-2005, 10:27 AM
You cannot run a 92 PCM in a 89 car. It will cause all kinds of problems. The PCM pinouts are different and the car will not run correctly.

I agree with David, the fuel pressure regulator is probably shot. Since it's dumping fuel, the regulator is allowing fuel in in excess of needed. You can put a vacuum gauge on the FPR and see if it holds vacuum. That is the only real test for it.

Also, make sure the fuel lines are not pinched. A pinched return line will DUMP fuel!!!

Change the PCM to either a 89 auto or manual or a 90 5-speed. The 90 auto PCM had no EGR and will run "OK" just different.


Don

scbird1
06-21-2005, 02:12 PM
Thanks for the replies. The fuel pressure regulater was changed and the correct ECM is back in the car. No pinched lines. The fuel dump is from trying to start this thing with every change we make we try to start it. Will keep changing oil till its figured out. Next will be a partial tear down. :confused:

fturner
06-21-2005, 02:36 PM
Double check the spark plug wires and make sure they are on the coil pak right.... if your using the Helmes manual (I think thats the manual) supposedly the illustration there has it wrong...........

Frit

scbird1
06-21-2005, 10:31 PM
Double check the spark plug wires and make sure they are on the coil pak right.... if your using the Helmes manual (I think thats the manual) supposedly the illustration there has it wrong...........

Frit
You right but the later issues have it right. I have a Ford service manual for a 89 tbirds. I have rebuilt 6 of these engines. Whats wrong with this engine has left many people scratching their heads. Every thing that makes it a SC checks out along with compression and fuel. I would like to get a sound clip so you guys could hear this thing. Got to get this thing going for Phil.

Phillio99
06-22-2005, 01:38 AM
Yeah Mark a sound clip would be a good idea, i feel like an idiot not being able to get this thing running, it would make me feel better if others heard what this car sounds like. Hopefully things will get workin soon.
Phil

MySCRocket1203
06-22-2005, 02:28 AM
i had a 1996 v6 lx rebuilt and the guys left a rag int eh oil pan. guess what, that did pretty much waht your describing. car didnt run for crap would start and chug and id floor it for fuel and it would die anyway the only way we figured it out was i got pissed and took a saw to my oil filter, filled with threads. has the bottm end been rebuilt? and before you asked i had the engine rebuilt cuz i blew the head gaskets cuz i drove it like tiw was an sc ahhaha :D

pearl95sc
06-22-2005, 04:04 AM
Mark, I may come by and lend a hand. I checked a lot out with phil earlier on in the year. I was thinking maybe faulty wiring between the ecu, and the other related parts. The injectors all ohm out correctly, the tps/iac were from my 94, know they were good. My only thought would be to use a meter at the ecu plug and see what the readings are there vs the readings at their correlating sensors/devices. The whole rag in the engine sounds a tad odd, but i've seen stranger things. I can stop over after work tomorrow for a lil bit, but I gotta get my 95 back together for the bash, and my sis's car back together before I go to the bash. Gimme a call, let me know if its all ok to swing on by.

MySCRocket1203
06-22-2005, 04:53 AM
[QUOTE=pearl95sc]The whole rag in the engine sounds a tad odd, but i've seen stranger things. [QUOTE]

yeah the rag is odd but i gotta tell you i wouldnt have believed it if i hadnt seen it the guys who do the work at the shop actually (come to find out later) botched an oil change and fluids check by leaving the radiator EMPTY!!!! the kid blew his engine. my car hasnt gone back

scbird1
06-22-2005, 05:18 PM
Mark, I may come by and lend a hand. I checked a lot out with phil earlier on in the year. I was thinking maybe faulty wiring between the ecu, and the other related parts. The injectors all ohm out correctly, the tps/iac were from my 94, know they were good. My only thought would be to use a meter at the ecu plug and see what the readings are there vs the readings at their correlating sensors/devices. The whole rag in the engine sounds a tad odd, but i've seen stranger things. I can stop over after work tomorrow for a lil bit, but I gotta get my 95 back together for the bash, and my sis's car back together before I go to the bash. Gimme a call, let me know if its all ok to swing on by.


That would be fine with me if you got the time. I dont know where I put your number but any time after 2:30 I will be home. Thanks, Mark

scbird1
06-22-2005, 06:18 PM
Well I found something. After trying to start this thing I was looking at the boost vac gauge and thought the line was off so I pluged it at the manifold right. Well I guy I sold a engine asked if I had run a vaccume gauge on this engine. I hadnt. Well I hooked up my trusty old vac gauge and I could not get more then 3 hg of vaccume :eek: Man do I feel dumb. I had checked over the entire engine as far as new gaskets I saw that someone a long time ago had installed new Felpro head and intake gaskets so I dismissed any leaks there but I could not keep the thing running long enough to check for or hear leaks but know im going to tear off the top half and replace the intake gaskets as it the only ones it could be. Im a old pro at linning up intercooler tubes with tbird88 gaskets plus I resealed the blower and drivers side intake. Im thinking the rear cork gasket of the lower intake. What else would cause low vac besides intercooler, tubes and blower? I know for a fact that all the vac lines are on and connected to the right things.

huckleberry
06-22-2005, 06:31 PM
i think it is electrical!! i had a similar problem . car stumbled and died on the road. hard restarting, and chugging, when i finally got it to stay running. stalling frequently. finally restarted and ran perfectly!!! i did nothing but keep trying to start it. something funny was that during the day the AC was acting up . blowing cold air. i thought the AC was done!! after the stalling problems and then running good after, i deduced that the starter solenoid which supplies the electrical to the run system was faulty . i replaced only that solenoid and the car runs beautifully since . cheap part try it before you take to much apart! if there is no change you have my permission the tear it APART!!!! add this to the strange but true section!!!

Phillio99
06-22-2005, 08:17 PM
Hey mark I have Alyn's number if you need it. Also, when i tried to get a vacuum reading from outside the car i got 2 or 3 in Hg as well. I have a gasket kit in the truck, I think there is some RTV in the back too.

scbird1
06-22-2005, 08:33 PM
Yep, I saw them in there. I have RTV black as well. It could not hert to do this as a last ditch effort. I will take a look inside the intake as well. I did notice that the plugs were black with soot when I removed them. I will let you know what I find out. Mark

scbird1
06-23-2005, 01:08 AM
Well looks like I won`t be home till 5:30 on Thursday. Well took the lower intake off and NOTHING :( Looks like another dead end. Even checked to see if the egr was holding vac. Nothing is out of place but when I brought the engine around to TDC on the compression stroke the cam sensor was off by maybe 4 degrees off but I dont think this is a problem. Only other thing is it jumped a tooth on the timming chain and monkeys are gonna fly out of my butt. Before I assemble it im going to check some of the wiring harnesses.
No fuel in the FPR and it holds vaccume. Put new o-rings on the injectors as well.

bdfnbrd
06-23-2005, 01:22 AM
crossed wires? that would be waaaay too easy but just a suggestion..

Sweet90SC
06-23-2005, 01:55 AM
Mine did that and it turned out I just didn't get my IC tubes sealed properly... :o

Phillio99
06-23-2005, 02:18 PM
It's to the point where the fuel system seems to be functioning like it should be mechanically. It's also to the point where all the ignition system has been diagnosed and is working the way it should as well, including the DIS, coil pack, cam and crank sensors, etc. Since the symptoms are flooding, bogging down and stalling it can be assumed that the computer thinks there is more air entering the engine then there really is, thus the computer sends a signal for more fuel. Which sensors does the computer rely on for determining fuel injector pulse width? MAF sensor TPS anything else? It can't be the MAF on this particular car because when unplugged the car doesn't run. just trying to throw some thought out there.
Phil

scbird1
06-23-2005, 08:52 PM
Here is the update. It runs the same after replacing the intake and injector gaskets. Nothing is cracked, no rags or blockage. Thing sounds like its running on 3 cylinders. I just canot beleave that this thing will not run right. Bring a gun Phil, I think we need to put it out of its misery :D

fturner
06-24-2005, 07:33 AM
You know I had a car do that to me once after I put a new timing belt on it, and it was cause the cam was 180 degrees out.............

You mentioned your thoughts about the timing chain.... and by the looks of it that's where you'd better look.

Frit

scbird1
06-24-2005, 07:09 PM
The only problem with that is these cars have a very good chain and with the tensioner it would be real hard to jump a tooth. The cover look original and has not been taken off but thanks for the reply.

huckleberry
06-24-2005, 08:46 PM
is the shift indicator light on during starting ? could be the speed limiter is faulty. and the EEC thinks the speed is eccessive.

scbird1
06-25-2005, 01:02 PM
Its been a tough go on this car but to many things could be the cause of this car not running right. at first I thought balancer because the weight was realy loose without the rubber holding it. When I dug farther I found a lot of wires under the car that had been put back together with speaker wire. Looks like the floor board had rotted out and caused some shorts at one time. Who knows what type of dammage it caused or if the wires are put back correctly. I dont give up on anything once I start but this poor car has seen its day :( Here are some of the pic`s Sorry Phil, I tried my best

MySCRocket1203
06-25-2005, 01:42 PM
hey i fond your problem your cars missing a supercharger ahhaa jk yeha that sux man whats uyp with the rats nest of wires there

scbird1
06-25-2005, 01:56 PM
If you look just under the wires you will notice that you are looking at my garage floor. This is in the drivers side floor pan :eek: Its a hole about 2 feet long by 8" wide. The last picture was oops. The engine is all back to gether.

Tickler
06-26-2005, 03:25 AM
how much vacuum does it suck when cranking? should be around 10.

Sweet90SC
06-26-2005, 05:40 AM
Its been a tough go on this car but to many things could be the cause of this car not running right. at first I thought balancer because the weight was realy loose without the rubber holding it. When I dug farther I found a lot of wires under the car that had been put back together with speaker wire. Looks like the floor board had rotted out and caused some shorts at one time. Who knows what type of dammage it caused or if the wires are put back correctly. I dont give up on anything once I start but this poor car has seen its day :( Here are some of the pic`s Sorry Phil, I tried my best


Ewww Yuck! I'm not sure I would have had the courage to even take on anything with an abortion of a wiring harness like that.. :eek:

Phillio99
06-26-2005, 06:20 PM
Cranking vacuum is under 5in Hg, more than likely in the neighborhood of two.

Tickler
06-26-2005, 08:55 PM
I just rebuilt half of my motor, and am having very similar trouble. I noticed that some spark plug wiring diagrams on the site are wrong. I did the wires as instructed, bucked, backfired, would barely run. 123(top) 564(bottom) is stenciled on the coil pack, tried it out, worked alot better, this trick might work for you, might not. Your motor should pull 10+ hg's when cranking, no wire or injector trouble should change that. I would look at the IAC or for a vacuum leak. The Dis has been known to kick the bucket from time to time, but a quick self-test should confirm.

scbird1
06-26-2005, 10:16 PM
Check this out. Last night I went to bed not feeling good at all. I woke up this morning to a dream I had. Guess what I was working on Phils SC and when resealing the tubes I thouht to my self humm some one must of undone the lower bracket, Them I had a vision of the bracket being broke off the lower tube. All day I have been to weak to jack up the car but tonight I was feeling better so I jacked it up. This is were it gets wierd. THE LOWER INTAKE TUBE HAS A HOLE IN IT ABOUT THE SIZE OF A SILVER DOLLAR WHERE IT BROKE OFF THE LOWER MOUNT. Weird huh Now to take off power steering brackets and all that carp to get to it. Dont count this car out yet Phil. Film at eleven

scbird1
06-26-2005, 11:27 PM
Here is what was wrong. you never know

scbird1
06-27-2005, 01:48 AM
Looking at how it broke was the result of a slight front end collision. Dave Dalke said it at one time, if your car has been in a front end collision check all your intercooler and tubes and he was right. Wow, what a hole. Got it changed and will fire it up tomarrow.

Phillio99
06-27-2005, 02:11 AM
Look at this, Im not on the forum for one day and Mark finds this. Just yesterday I was thinking about how i was going to part the thing out. Mark what a find, I knew it was a vacuum leak!! Wonder if thats whats causing t3in Hg?! Well im pretty excited i really hope thats what ive been chasing for 9 months now. By the way, get some sleep.
Phil

David Neibert
06-27-2005, 09:04 AM
That's a big vacuum leak...glad you finally found the problem. I'm sure the car is going to run much better now.

David

SCTIM
08-18-2005, 05:16 PM
Thats A Nice Size Hole,,,thats A Easy Fix, Now What About The Floor Pan???

XR7inWI
08-18-2005, 06:08 PM
OK, Since this thread has been resurected... I gotta know.... Did replacing the IC tube solve the problem? I assume it did as that was a MASSIVE vacuum leak but was just wondering if ya got the SC runnin'? If so, it must be getting a little rust repair now or in the near future, huh?

scbird1
08-18-2005, 06:27 PM
It ran after that but has had many set backs as the trans went soon after. Not shure whats going on with it now? Maybe Phil will chime in here. I have been up to my elbows in a F body as of late but thats another story.

Phillio99
08-18-2005, 06:27 PM
Yup, been patching up that rust hole and got that wiring harness tucked away. Thing runs great now, has a little stumble at idle, just need to change out the 02 sensors and I should be golden, otherwise car runs great pretty quick too.
Phil