dansam

Ok here is my problem. I have an 89 GTA 350 w. lots of mods (comp cam headers ported, polished heads, intake and plenum, the engine only has like 5000 miles on it). It is running great except for when you go to WOT at that time it sounds like it has no fuel delivery. I thought maybe I fried my Jet chip so I put it back to original but no dice. I also get a trouble code for the egr valve but Ive gotten that forever and it never seemed to effect anything. The only new thing would be the electric water pump I installed on it. I direct connected it to the battery to confirm that was not the culprit, also it does this hot and cold. I retimed the engine and everything checks out ok. I can bring it up to redline as long as I dont floor it. What gives???????

dansam

I have not checked fuel pressure yet (thats next). Fuel pump makes noise on startup though and response is pretty good if you dont floor it.

Dan

lordmetalz28

id try getting a new performance fuel pump if its old and stock chances are it cannot keep up with demand. also first thing is changer your fuel filter defiently.

aklim

Hook up the fuel pressure gage to the schraeder valve on the fuel rail and tape the gage end to your windshield. Turn the switch to run and see what pressure you get. Turn it off and wait for a while to see if you are losing fuel pressure. It should hold pressure for a long time (several hours). If all is well there, your FPR is not the problem. Run the car and watch the fuel pressure. If that is ok then do a WOT and see how far it drops. It might drop a little but should settle at a pressure. If it does, the problem is not in the pump.

The problem might be your Jet chip. It may not be set for that particular condition you have. If that is the case, www.fasterproms.com does a truely costom chip. It will take them several weeks because they will burn the chip, have you take readings and reburn 2 times more to get it dialed in perfect.

dansam

Yea I need to pick up a Fuel pressure gage Monday. I took the jet chip out so that it is just the original chip in there and the problem is the same. The fuel pressure regulator was swapped out for a new one like 5000 miles ago with an adjustable one (Not only swapped the cap, I swapped out the juicey insides as well) that I never got around to cranking down as the engine was still in break in mode. Now that its broke in and I want to really hammer on it (Ok I may have opened her up a few times allread, and never had any trouble) WOT is inop. I wont be able to hold it open to Wot for long for the fuel pressure test as it sounds really bad at wot and I dont want to burn one of my new valves! But Ill try and find out. I figured it was the chip (not) the distributor (havent checked yet) or the fuel pressure (what Im betting on). Soon I will know. I must say though that this is a PIA, and as much fun as the car is it is the end of the season and I only have one event left to go to on Oct 11th at auto city and Im done for the year. I guess I should be happy I got most of the summer with it.

Dan

aklim

If the fuel pressure is good and the spark is good, it may be a calibration issue. The Jet chip and the OEM chip may not be doing it for you at WOT. AFAIK, at WOT the ECM ignores all sensor readings and does not compensate. It just goes off the programming and if the programming is inadequate, it will simply use it. If you have eliminated everything, maybe the last thing to try is a custom EPROM instead of some off the shelf unit. I did and am happy with my results.

dansam

With its current setup sans E water pump it had WOT no prob. While a custom chip is a future mod and no boubt would help performance a bit, it is not THE current problem. It is either fuel or spark. Im betting on fuel. Ill know soon I pick up the fuel pressure gage monday. Ill let you guys know what I found.

Dan

aklim

How about hooking the elec WP to the battery directly and see if it has that problem?

dansam

Ok yea I tried hooking the wp to the batt no diff.

I replaced the pump and fuel filter and well, its still doing it !!!!!!!!!!!!

Im really getting pissed. Im thinking the only thing left would be a ECM failure or maybe an egr valve??? Dist prob???

Runs strong till you mash it then it falls on its face no WOT at all. Can rev it to 5000 real strong as long as its not floored.

Maybe something happened that effected the FPR. Ill get that damn fuel pressure gage. I thought Id just replace the pump and avoid the extra expense (fooled me).


Any IDeas???? Anyone........bueler bueler.................

aklim

At WOT, egr is out of the picture. Do you have a scanner where you can monitor the O2 sensor? That would give us a clue if it is running lean or not. I assume the plugs are good. How about swapping a known good coil and see if that makes a difference since there may not be enough juice to spark it that many times in such quick succession. Also another thing to try is the ignition module in the dist. Do check out the spark and see if you get a strong blue one when you rev it up at night.

dansam

Ill try all that stuff, I usually can get a scanner from some friends for a weekend. Im going to get a fuel pressure gage today so that I can rule out the regulator. Truthfully Im going to take a few days off fixing it as the fuel pump took allot outa me, and cut my hands up pretty well.

thanks Dan

dansam

It was the MAF sensor..... whodathunkit.

Dan

aklim

How did you figure it out? Was there a hard code or what? Just trying to learn something new.