FlyboyZ28

When i drive my car for short periods of time the car feels fine. The car gets up to its normal temp. at about 160 and will be fine. But after about 20 min. or so the car starts missing vilolently in lower rpm ranges and when i decelerate the exhaust starts to pop. When this is happening the temp rises a little above normal to about 190. Its not overheating but runs hotter than usual. I don't know if this has anything to do with it, but it has rained a lot here lately Over 6 inches in the last couple days. I havent really driven it while it has been raining, but my car sits outside during all of it. I know a lot of people are going to say opti, but the car has the vented opti conversion on it, and was changed when the motor was built about 7000 miles ago. Thanks in advance for any help.

Dan

Guest47904

Sounds like you may be having a heat related breakdown to an ignition component. My first guess would be the coil. Look very carefully at it for tell tale marks on the outside of the coil. You could also do a little experimentation with a blow dryer. When the engine is dead cold, start it up for a second or 2 to see it's running ok. Then shut it down and get the dryer and warm the coil to the point of just too hot to touch. Now start it up and see if it runs bad.

If it runs bad, you found the bad part. If it runs good after heating that part, try another. Like the ICM with the same process.

Another thing you can try is use an inductive timing light to see if you can see a difference in the flash pattern when it begins to run bad. Depending on where you see the difference in the flash pattern can help pinpoint the problem.

Don't forget the wires and plugs as well.

FlyboyZ28

Changed out the coil, and still the same problem.

LilJayV10

I looked at his car tonight, I am the one that built the engine and put it in the car. It took about 15 minutes of normal driving before it really started missing really bad. I had him hold the car in gear and push the gas down and the brake till it started missing. Looking under the hood the header tubes on the passenger side are all glowing red. When you let off the gas and let the car idle they stop glowing, but the longer you make it miss the brighter the header tubes get.
I wouldn't think it would be a bad injector because it's all four cylinders on the passenger side.

I wouldn't think it's a fuel pressure problem(which I am going to check tomorrow)because again it's only on the passenger side.

In 93, isn't it a batch fire fuel injection setup, it fires the driver side then passenger?

I attribute the engine temp going up due to the fact that it leans out, when the headers start glowing.

Right now I don't have a good answer or direction to go from here, besides checking the fuel pressure tomorrow.

93yellowta

yes the 93's are batch fire. first one side fires, then the other..

FlyboyZ28

Then what would cause only one side not to fire?

FlyboyZ28

ttt Please.Nobody seems to know where to steer me.

FlyboyZ28

I also posted this on speeddensity.org If anyone is interested here is the link.
http://www.speeddensity.org/showthread.php?t=1417

thanks
Dan

matLT1

It sounds as though your car is running lean on the passenger side only. Something that may be worth a try is to swap the 02 sensors from one side to the other. I'm not too sure if the right 02 controls the amount of fuel for the right side and the left 02 controls the amount of fuel for the left, but if it does and thats your problem, swapping the two should swap the glowing headers to the drivers side.

FlyboyZ28

ttt

FlyboyZ28

I'm still working on this. We have checked the fuel volume and to us it seems a bit low. I have an extra Walbro 255 pump laying around so I guess we'll be putting a fuel pump in soon. The problem we noticed is that when we let the engine run the number 2 cylinder ingjector doesnt fire as hard as the rest of them when you put your hand on and feel. I switched the wiring harness plugs on the injector and its still the # 2 firing weak. I took the fuel rail up and switched the injectors between # 2 and # 4 and the different injector in the #2 slot was the one firing weak.

anyone have any ideas on this

thanks
Dan

FlyboyZ28

Oh, and by the way there is some interesting discussion going on about this at the Speed Density Board. If anyone would like to take a look. Here is the Link:

http://speeddensity.org/showthread.p...4749#post14749

LilJayV10

ttt. still haven't fixed the car. It's in the air and the tank is ready to come out. It has a racetronix pump in it, the one thats modified to fit the stock setup.

I will give some more info, maybe it will help.

you can drive the car and it will run fine for about 10 miles or so. then it starts missing at low RPMS and the car bucks really bad. If you give it more gas and the RPM's go up it smooths out and runs fine. It gradually increases, the higher the RPMS that it misses at, the more throttle you have to give it to get it to run. It comes to the point that you can have it to the floor and the car will only go 15mph. It bucks and misses out of the exhaust.

I checked the fuel pressure and it's fine, never changes. I am wondering if it's a volume problem. How do you test the volume correctly? Do you block off the return line and let it pump into a bucket or something?

It's 255lph pump, divdine that by 60 minutes in an hour and you get 4.25, does that mean it should pump out a little over 4 liters in one minute? Am I looking at that right?

I appreciate any help. I really have no idea's.

I also replaced the ECM, didn't change anything.

93turbo5oh

my car did the same thing. my 6K mile, 1 year old walbro 255 had taken a ****. it would get hot and lose fuel pressure. put a new gm pump in and havent had another problem.

Stroked94z

My car did the same thing after we put the head sand cam in and we literally replaced every sensor and it still didnt fix the problem. But it ended up being the heat sensor in the front of the block that was bad. When they go bad, they tell the computer that the engine is running too rich so therefore it cuts the fuel back. This might or might not help you, but every little bit of info helps! Keep us posted and let us know what it is. good luck man.