Bogging/Hesitation - Opinions? [Archive] - Forum


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07-11-2005, 12:55 PM
Well the latest in my sisters fun GAGT saga...her car is such a lemon! She has 50,000 miles on her 2002 GA GT and has had numerous problems in the last few months.

Anyway, the latest is hesitation, that has gotten much worse. So bad in fact she didn't drive the car home and left it at my parents. I went down Sunday to look at it.

I put a new fuel filter on, cleaned the IAC (was very dirty), and checked but did not clean the MAF. Did a MAF relearn. After this the car ran MUCH MUCH smoother. (it was surging idle, and racing a bit.) I didn't check the TPS but figured I may just replace it seeing as though its about 25 bucks.

Just a few weeks back it was at the dealer to fix the PASSlock and they "fixed" the hesitation with a top end cleaning/carbon cleaning. (Missing the IAC apparently.) It was no better when she got it back.

Anyway, now the car barely makes any power when accelerating. At times you can floor it and get no acceleration.

While I didn't check the TPS I don't think this is the issue. The car will rev up find in park or neutral with no engine load. The IAC should be fine as it reacts normal when load is applied (like when the AC is put on in park, it adds a few revs which it was not doing before.)

Anyway, I suspect a fuel problem. Possibly a pump going bad, bad fuel pressure regulator, or maybe even just real dirty injectors.

I did notice when turning around, if I hit the gas immediately it would bog down immmediately. If I stopped and let it idle about 15 seconds it would have much more power, which tells me perhaps the fuel system isn't getting enough pressure but letting it sit at idle allows the system to build pressure.

So I've read alot of people with hesitation having bad fuel pumps, and fpr's, just curious what you guys thought about this.

For the longest time she's had a hesistation...the car was not very responsive until over 3500rpm. (Hence the carbon cleanout and new fuel filter.) She has brand new plugs and wires too which didn't fix that.

She's probably taking into a shop but we all know that doesn't maen it'll be properly diagnosed. To help that out I've told her to request they check the fuel system pressure and while they're at it go ahead and check the TPS voltage. (Since I didn't...even though I doubt it's a TPS problem as it runs fine iwth no load...or am I wrong in saying that?)

Jsut curious...

At anyrate I think her plan is to trade the car in once it's actually running well enough. She really got a lemon though, mine ran fine for 83,000 with no major issues at all.

07-11-2005, 02:59 PM
Scan tools are invaluable in a situation like this. With a computer controlled vehicle, there are many many thing it could be. I think your on the right track looking into fuel delivery. Use some electrical contact cleaner on the MAF, that might help clean that up. Also, here might be a clue, how does it run when its started cold? A car that acts totally different when running in open loop (cold start, WOT) than in closed loop (warmed up, normal driving) can indicate a problem with the 02 sensor. Oh, here is another big clue... how is the shifting? A bad MAF, IAT, or TPS sensor usually has some bad/odd shifting associated with it, so that might be another clue. Just some thoughts.

07-11-2005, 04:24 PM
Here is a TSB about the COMMON dirty fuel injector issues with GM cars. I had to cut most of it off, but you get the idea.

Multiple Driveability Symptoms Due to Clogged Fuel Injectors (Clean Injectors) #03-06-04-030A - (Jun 24, 2004)
Table 1: Example One
Table 2: Example Two
Multiple Driveability Symptoms Due to Clogged Fuel Injectors (Clean Injectors)

2000-2004 2.2L, 2.8L, 3.1L, 3.4L, 3.5L, 3.8L, 4.2L, 4.3L, 4.8L, 5.3L, 6.0L, or 8.1L Engine (VINs F, 4, 8, J, E, 6, K, S, X, V, T, N, U, G - RPOs L61, LN2, LK5, LG8, LA1, L52, L36, LL8, LU3, LR4, LM7, LQ9, LQ4, L18)

and Multec II Fuel Injectors

This bulletin is being revised to update the procedure, models and model years. Please discard Corporate Bulletin Number 03-06-04-030 (Section 06 -- Engine).

Some owners may comment on driveability symptoms of long or hard starts, chuggle, rough idle, hesitation, and light or intermittent misfire. The malfunction indicator lamp (MIL) may also illuminate.

Due to various factors, the fuel injectors may become restricted. Extensive testing has demonstrated that fuel related issues are the cause of clogged injectors. At this point, no specific fuel, fuel constituent, or engine condition has been identified as causing the restriction. The restriction causes the engine to operate at a lean air fuel ratio. This may either trigger the MIL to illuminate or the engine to develop various driveability symptoms.

Fuel injector restrictions, deposits, can be cleaned on the vehicle using the following procedure. Under NO circumstances should this procedure be modified, changed or shortened.

The recommended mixture amount of GM Top-Engine Cleaner has been increased from 5% used in prior procedures to 10%. This increase was implemented to improve the effectiveness of the injector cleaning procedure. Follow the cleaning procedure carefully to minimize the risk of fuel system damage. Testing has demonstrated that exceeding the 10% cleaning solution concentration does not improve the effectiveness of this procedure. GM Top-Engine Cleaner is the only injector cleaning agent approved for use with General Motors fuel system components. Other injector cleaners may cause damage to plastics, plated metals or bearings. General Motors has completed extensive laboratory testing of GM Top-Engine Cleaner, and can assure its compatibility with General Motors fuel system components, as long as the cleaning procedure is followed correctly.

This bulletin recommends the use of pre-measured containers of GM Top-Engine Cleaner, P/N 12346535, - U.S. USAGE ONLY. Pre-measured containers eliminate the need to measure the amount of GM Top-Engine Cleaner being added to the J 35800-A, injector cleaning tool. In Canada, use P/N 992872. It will be necessary to measure and dispense Top Engine Cleaner into the J 35800-A, injector cleaning tool.

07-17-2006, 05:07 PM
ok so my car surges sometimes while in park and thats all. no hesitation while i am driving i dont think. the solution to this is to clean your fuel injectors? i'm also thinking about replaceing my fuel filter. my spark plugs were replaced about 8 months ago by myself so i dont think that is the problem. can i clean the injectors myself? or am i better off letting a shop install my fuel filter and cleaning the injectors.

07-19-2006, 04:45 PM
can anyone help me?

07-19-2006, 06:18 PM
ok well i put prestone injector cleaner into the tank and it seems to be doing alright in park now! further driving will tell me forsure though.

07-19-2006, 07:41 PM
i got this thing done back in january when i was getting my oil cost like $65 to clean the whole fuel system,was well worth it

07-19-2006, 08:40 PM
seafoaming the whole thing may or may not help the problem, but if you've got some serious miles on i'd recommend it.

07-20-2006, 08:25 PM
also make sure to check your spark plug wires are all the way on! haha. I was checking my maf screen today and decided to check the spark plug wires. one was almost off! DUH

09-26-2007, 10:29 PM
Sounds like my car when the CAT was clogged. Replaced the cat, and ran like new.

Got an aftermarket one, because the OEM is expensive.

Did you ever figure out what was wrong, or did you get rid of the thing already?

-Just wondering

10-04-2007, 10:32 PM
not to sway to far from the topic, but is there more tests to figure out if its a clogged cat. before screwing around with other things, mine has a little hessitation

10-08-2007, 10:00 AM
Okay, the other day i just did a pan/filter drop in my tranny and took out the bosch +2's and put in NGK Iridiums IX, Now my car pulls hard all the way up to 6K, before it would go past 3,500RPM and not go anywhere. Try a tranny flush.

10-08-2007, 04:45 PM
mabey just start with checking the tranny fluid

10-23-2007, 08:24 PM
my car hesitates only sometimes when it is moderately cool (below 150F). when it warms up the problem seems to disappear. it misses a little when its idling and when i give it a little gas. but it doesnt hesitate at all it seems above 2000 rpm. (3400 v6 engine btw)

did the following things to try and fix it:
-techron fuel system cleaner
-new irridium spark plugs
-cleaned maf sensor
-cleaned TB
-cleaned and re-oiled air filter

i dunno what else to do. im pretty sure my CAT is ok because the car backfires a lot when i let off the gas. ive got cold air intake with huge k&N filter and i cut off my muffler and put a straight pipe so im sure its not too restricted. the spark plug wires arent corroded at all. i checked for arcing one night when it was dark and i didnt see any of that. i got my fuel pressure checked so i know the fuel filter and fuel pump is ok. i think the car is running lean because i did a tb coolant bypass, which is after the maf of course. and so the computer is giving the engine an AF ratio for warmer air i beleive. but would this cause my engine to miss? also might be the IAC but i read that a lot of people replaced it and still had problems. i dont have an SES light either. what do u guys think?

10-23-2007, 08:31 PM
have you checked for intake mani or gasket leaks? BREADFAN????

10-23-2007, 08:45 PM
hmm i might try that. any suggestions on how to test if its leaking?

10-24-2007, 06:42 AM
use a vacuum gauge or spray all around the intake LIGHTLY with t.b. cleaner