I posted a while ago in the transmission boards thinking that was the problem...im moved away from that...then i thought it was a clogged cat...stopped thinkin that too...heres the story

last week my car started actin funny...you jump on it, and depending which gear it downshifted to, it would run up to a certain spot then hold it at that rpm, not shift, but not make power either. 1st gear it will go up to about 4500 and stop, then begin to buck and bogg, and in 2nd it will go til about 3500 and bogg there too. it will only shift if i let off the gas, but thats expected. i thought it was a clogged cat, but i took it to the shop i go to, to get my exhaust installed as well as this problem diagnosed. well, i went in today hoping to get the car back, and my exhaust was done. i popped the hood, headers looked great. my set up is hooker 2055s, catco, hooker cat-back. the guy who road tested after the install still felt the problem i had before. now im stumped as to what it could be, and the car wont be getting worked on like that until i assume tomorrow. i just had the fuel pump replaced about a month ago with the fuel filter, the 02 a few months ago, tranny fluid 2000 miles ago (thats all ive really put on the car since ive had it in september)...its throwing no codes.

my 3 guesses are clogged filter somewhere, ignition problem somewhere, or a fuel pressure problem. please let me know if any of you have had similar problems, or know what it is. thanks.

 

Tranny related being, torque converter or tranny itself thats just my guess I cant really help you out since im a stick shift kinda guy but if I were to diagnose something its tranny related 4 sure. Good luck.

 

i really dont think its tranny related, from what ive seen with tranny problems the rpms will go up but the car will go nowhere, my rpms stop before they reach their normal shift points, which is where it seems like the engine cant breathe or loses fuel pressure.

 

Agreed...there's SOMETHING holding your motor back. Will it free rev to or past your normal limit? I imagine it will.....

 

Nope. The rpms just flat out stop, it stops revving when it reaches that point, like thats the only way it will stay alive is if it stays at that rpm or lower...

clogged fuel filter is what im leaning towards...the fuel will flow fine until upper rpms where the engine wants it bad...in which case there is somehting there preventing the fuel to flow that much...thus the engine cant run that high...thats me and my limited engine knowledge...all of your input helps.

 

If it does that not even under load, then it sounds MORE like a fuel problem to me than ignition. I'm leaving out the third key component, air, because......unless you have a sock stuffed in your TB, I doubt air is a problem.

I'd say you definitely might be onto something. Fuel filters are cheap--replace it and see what you get.

 

If the RPMs at which it did this varied with load, I'd say fuel.

Since you say it happens at the same RPMs regardless of load, that sounds like ignition.

Coils have been known to go weak, as have ignition control modules. Arcing cap or rotor will do funny things.

 

Here is the diagnosis...
the fuel filter is fine...however, at idle the fuel pressure was at 32 pounds, then when you step on the gas it drops to 20....

the one mechanic who told us this believes its my new fuel pump taking a crap, or a fuel pump relay problem

so i go to the shop that installed my fuel pump, and he says it doesnt sound like the pump, and he strongly feels it isnt...

i think its my fuel pressure regulator, or something of the kind...

feel free to jump in and say what it could be....thanks guys

 

Wow, some quantitative data!

Except, how do you know the fuel filter is "fine"?

Did you check the pressure with the vacuum disconnected?

Was the pickup sock changed when the pump was changed?

Sounds more like the pump. At least the EFI vehicle I have showed similar pressure symptoms with a bad pump. Which was a new one, by the way.

 

The fuel filter I know was fine because the mechanic took it off and blew through it...so it was ok...

to answer your other questions...i havent a clue...you did indeed have bogging at higher rpms when your fuel pump was going bad?

 

No, I said I had similar pressure symptoms.

My worst operating problem was the car was nearly impossible to start. It could be nasty soon after starting as well. After running, it was typically fine. After putting in another (of a different kind) new pump, it's been great.

(This was a '91 Pontiac Bonneville w/3800, by the way.)

 

See thats what happened to me earlier when the pump first went out...i had just got done driving for about an hour...turned it off for 5 minutes, came back to it, and it would start but stay below its normal idle and die...

now, it will start beautifully, and be beautiful unless i get on it...if i get on it it will refuse to pass a certain rpm...normally when its 3500-4000 range like i said...if it helps at all:

the morning after the problem arose, it was chilly outside, instead of blistering hot like it has been, and she ran beautifully, redlined and shifted every time just like she always had, but as soon as the temp read about 160ish...it began acting like it always had.

 

Pump.

The symptom for the pump that preceded the bad replacement was hard starting and no power at all when it got warm (drove home at 40 mph on a 65 mph speed limit freeway - fun...).

 

hello guys,my car have same problem-in cold engine would
rev 6500 rpm very nice-but after it have warmed up, it would
not rev more than 4000 rpm. not even park or neutral-like
rev.limiter hit on...very strange. my car gives ecm code 43.
so i try change est/esc module.and knock sensor (distibutor shaft and ignition
module is new) so if it does not help i have try new ecm.
if i m succesful,i let you know.
and my car is 89-trans am gta 350 tpi with plenty of modificatio
4 bolt zz block, lt4 hot cam,ported manifold,slp runners, 52 mm
tb. edelbrock tes. headers,ported vette heads,(0,525 lift 280
cfm 28") 36 lbs injectors.3" exhaust with straight mufflers.
and not kat needed in finnland...

 

I thought that TPI was supposed to run at 3.5 BAR (3.5 times barametric pressure, a metric unit, man, I wish the french diden't think that system up ~50 psi) as a baseline?, I'd test the pressure before the reg. to see if the pump is putting out, it should be like 60+ psi., and the reg. should let it down to 45-55 psi. depending on the vacume signal it recives. just my $0.02

 

sure sounds like a bad fuel pump to me. i'd do the pressure test and see what you really have and go from there. along the same line are you sure the tune up is good? most of the parts are cheap and easy to replace.

 

hello again,do your cars give any trouble codes?
last week my car goes grazy,i was driving highway and
ses light start burning continuosly and soon car beheaving
like cut of-i could drive home-and check codes :21,34,42...
now it is very difficult to start-and its running roughly.
i havent get new est-module yet- mayby ecm has died...