I have an 89 camaro with a fuel injected ZZ4 in it. The motor itself is pretty much bone stock. There was a 5 speed conversion done to car itself but shouldent have any effect on the performance of the car, the carburator is off and was switched it to fuel injection. It has a custom burnt chip in it but besides that its all stock. I bought it a year ago and it was running great. Then I progressively noticed that after I ran the car for a while I would go to get on it and it would jump as if it wanted to go but instantly violently bog down to have no power going to the motor when my foot is down on the peddle at all. It seemed like the car was in neutral when it was done jumping. When this first would start to happen i would push in the clutch obvisouly, but what is odd is that when i disingauge it i could rev it as high as i wanted. The funny thing is that before when I first started noticing it, it would happen only occasionally, now and I can go start it up and have the this problem immediately any time I try to drive it. I have taken it to a handful of shops and they couldn’t tell me anything on what is wrong with it. It has been on a dyno with nothing and a computer with nothing? I have had a person tell me that they think it’s a mass airflow censor but I don’t want to go fishing in my motor hoping I find the problem. Also theres a leak from my y - pipe in the exhaust but i dont think thats my problem and i recently put flowmasters on it and the muffler on it is huge, wondering if its getting to much back pressure when i go to get on it causing it to loose power?. I’ll take any suggestions I hate not being able to drive it ya kno! If you know any good speed shops or anyone who works on ZZ4's in or around southeastern pa please let me know.

 

I don't see any mention of fuel pressure. Check it, and monitor while this is occurring.

And it's not a lack of backpressure. Get that out of your head, and don't let anyone say it is.

 

Well, it could be a back pressure issue but not in the way he's thinking. Is this car running cats? If it's plugged then your running a ton of back preassure and that could be your issue.

Any more info on the car you could supply?

 

When i put the exhuast on they hollowed out the cat and also he told me the y pipe had a leak in it. The biggest problem for me is that the previous owner never gave me alot of information on the car and i have no way of getting ahold of him. Thats what all the shops have told me. I have heard that a lot of people who have tried to switch the zz4 over to fuel injection have had lots of problems and fuel issues with . Do you think it would be worth it to switch it back over and if so how much?

 

Na, I think people are telling you things without first knowing whats going on. Being a ZZ4 should not make any difference. If anything, it would probably be a fuel issue if this system is designed say for a 305. As five7kid mentioned, check what your fuel pressure is. Also, what FI system are you using? Since you say its getting worse I would think something on the line of a fuel pump or clogged/failing injectors.

 

Does you r car have a catalytic convertor in the exhaust? If so it may be plugged up. These same symptoms showed up in my 93 jeep grand cherokee, and it was the cat. It plugged up and was forcing the motor to overheat. I do mean plugged up almost all the way. So I had it replaced along with the y pipe, cause the back pressure cause a crack.

 

What fuel injection system is on the engine? Most aftermarket systems don't use a MAF sensor. Does it still use the original ZZ4 HEI vacuum advance distributor or something else?

Most shops don't know what to do with an aftermarket fuel injection system. Don't expect much help from them. I couldn't get a shop to touch my supercharged Corvette. If you can't solve this on your own then you need to hunt down a custom engine tuner that has lot of hands on time with racing engines and fuel injection systems. Some dyno shops will have a person on staff with these skills.