i have just installed a new fuel pump last week. the car ran fine up until two days ago. now under certain throttle settings the engine surges, stumbles and generally won't hold a steady rpm. load or no-load makes no difference. sometimes when i take my foot off while it's doing this the tach will nose dive and pick back up. it still idles just fine and i haven't noticed serious stumbling while accelerating. just during steady throttle. no codes have been set. i put the computer in diagnostic mode and varied the throttle with the same results. i think that eliminates the knock sensor and ESC. i sprayed liberal amounts of carb cleaner down the bores and IAC passage already. timing seems ok. the car never acted like this before. one more thing, when i put the car into field service mode (according to the manual) the car was in open loop mode. the engine was at normal temp and everything else seemed ok.

does anyone have an idea before i go crazy?

thanks,
Ray

 

did you reset your computer?
Im going out on a limb here and would like someone to verify my theory, but maybe your computers blm has adjusted so much to a slow or bad fuel pump that now it doesnt know what to do with the new increase in fuel?
But then why would it run fine for a few days first.
But, even still it wont hurt anything to reset the computer(by unhooking the battery).
But again, you probably did that when you replaced the pump huh?
Ok new idea, fuel filter is now clogged because crap got int othe fuel line after installing?
Also maybe go buy a bottle of injector cleaner/ fuel system cleaner. again, wont hurt, and would be good for your car anyway.

Finaly, maybe you just got a bad fuel pump.

Sorry hope somebody else can help more, I just kinda threw out some ideas didnt I.

Maybe you should tell us why you replaced it.

 

i'll try that. i changed the pump because the original was giving out. it sounded like it was full of kitty litter. when i pulled it the tank is clean as a whistle, so i gutted the pump and found out the brushes and bearings had simply worn out. thanks for your help.

anybody else have any suggestions?

 

I've been doing a search for this type of problem, and yours sounds just like mine. Same type of surging, rpms rising and dropping at idle.

I've replaced the filter, Throttle Position Sensor, Coil, Air Speed Idler, TBI intake gasket, checked the lines for any vacuum leaks and replaced the fuel pump and the 2 injector fuses.

I'm not getting any service engine lights and have no diagnostic tool to check for any codes. The injectors spray just fine,I've thought about it being the fuel pump, TBI needs adjusting or maybe the timing is off.


------------------
Evil's 88 Camaro
Stock 305 TBI Auto, Flowmaster, Full 3" Exhaust, B&M Megashifter, K&N Open Element, MAC Lower Control Arms and Panhard bar

 

my car was surging because two plug wires were burned, they also sent signals to the tach and made the needle bounce.

 

Thats possible, I replace the wires about 3 years ago. Did your wires have actuall burn marks on them?

[This message has been edited by EVILFACE (edited June 10, 2001).]

 

parts of them were blackend about a cm long. They were very close to the exhuast maniflod. I bought new wires and plugs, rerouted them, and my problem was solved. by the way I didn't have a "check engine light" so I wouldn't have gotten any trouble codes. inspect all the wires closely and let us now what it is. Hope I helped.

------------------
late model 91 rs
fully loaded t-tops
red leather
paint- gm red and yellow blend (light red)
custom pink rims
305 tbi 14"x3" O.E,
computer chip, accel super stock plug wires
MTX sub and amp (very loud)
vic_v8@yahoo.com

 

Havent replaced the wires yet, but I did put on a new coolant sensor for the hell of it.

Something I did notice is that there is a vacuum line coming off the back of the TBI going up to a sensor I guess on top of the firewall below the passenger wiper. Anyone know what this is? If I pull the the hose from the TBI, the car will go into a normal idle and the check engine light will come on. But if I put it in gear, the car instantly dies.

I'll finally be taking the car to have it check tomorrow.

------------------
Evil's 88 Camaro
Stock 305 TBI Auto, Flowmaster, Full 3" Exhaust, B&M Megashifter, K&N Open Element, MAC Lower Control Arms and Panhard bar

 

This is an interesting thread ..... 2 people with the same problem, and now you can add a third.

I've been dealing with the same type of surging problem for a while now. The way you described how it can almost stall when you jab at the gas pedal sounds just like my problem.

With my car, the problem only arises when the computer goes into closed loop operation. In open loop, it runs great -- no surging or wierd RPM issues. This makes me think it is definitely a sensor of some sort?

Hopefully, someone else can shed a little more light on this,

Thomas.



------------------
1992 RS Camaro - Red
305-TBI/5 Speed Manual- 3.08 geared rear
1.6 Roller Rockers / Adjustable Fuel Regulator with high flow pump / Open Air K&N Filter / TBI Spacer / ADS Super Chip & custom burned Off-Road Only chip / MSD ignition
Headers - Flow Master - dual chrome tips
adjustable Coni shocks & struts

 

HERE IS CAR NUMBER 4!


Sorry, but on a lighter note mine does the same but only after very heavy rain or a power car wash.

------------------
--Spyder--

1992 Camaro RS
LO3, T-56,centerforce clutch, ported and polished 305 TPI heads, Edelbrock Performer Intake, 14X3 Open Element w/ K&N, hiflow cats with two pipes going back, AC delete, SMOG delete, alu drive shaft, 3.73 posi, 170 stat w/ fan switch, MSD Igniton Coil, STB, Subframe connectors, KYB AGX, Eagle GSC, and poly bushings.

1982 Z-28
Blow Motor, this July 350 4 bolt, ZZ4 cam and heads and the rest to still be purchased.

 

Add mine to the list also, it didn't do it when I bought it a little over a year ago, but for the last couple of weeks its been surging and trying die at idle. It runs great when it is cold, but when it gets warms it starts surging, especially sitting in the bank line, or at a fast food restaurant when the cars gets warm enough for the fan to come on. It will sit and idle rough, and when the fan comes on it will almost die, then surge up about 300-400 RPM and sometimes even try to pull through the brakes for just an instance, and then start idle rough again. It has actually died a couple of times, but cranks right back up, and seems to run better for a minute or 2, then starts running bad again. It also surges sometimes at part (not WOT) throttle when accelerating. I'm glad mine's not the only one, so if either I, so someone else figures this out, we ALL won't have to go through buying 5 or 6 sensors, chasing this problem. Mine's showing no trouble codes and no "check engine" light, it's just running like A$$ at random. Weather doesn't seem to be much of a factor.

Maybe Y2K for TBI is here, just LATE!!???

------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: first pass- 11.78 @ 112.83, 7.48 @ 91.94, 1.641 60' time


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

i read an article in underhood digest. it was refering to a foreign car, however, warmer air can mess with your idle air control if the map is off, or if your iat is off. anybody here having the prob done the resistor swap for the iat.

also the guy whose problem revolves around h2O. sounds like your dist is getting wet.

 

Snuf, good thinking about the distributor getting wet. Maybe it might even be related to the ESC getting wet? As far as the surging problem goes, I used to have trouble with the way my car ran. Sometimes it would idle irradically, and sometimes even die and it would never start again after that until it sat for a while. Turns out it was the CTS. The thing looked rotten inside and was rusty. Couldn't tell till you removed the connector. Never threw a code either. Intermittent problems are always the hardest to solve. One last suggestion, maybe a TBI rebuild kit would help?? It's out on a limb but I dunno. Goodluck!

 

What is the MAP sensor and what does it do?

------------------
Evil's 88 Camaro
Stock 305 TBI Auto, Flowmaster, Full 3" Exhaust, B&M Megashifter, K&N Open Element, MAC Lower Control Arms and Panhard bar

 

Well, last night, on my way home, the "Check Engine Light" came on and it started running very "doggish" (yes, that is a technical term ) I'm thinking the ECM went into some sort of limp mode or something?

I stopped to get some smokes & a six pack, and decided to checked under the hood before I shut it off. I wanted to see if I had any arcing going on (plug wires, distro cap or something?) but nope, all looked good.
So I come out of the store, start it up, and it ran fine for the rest of the way home.

Whoever said something about it happening when it gets hot, is right on. This problem never seems to show itself unless my temp gauge get over 160' or so. This is another reason I was thinking it is an Open Loop vs Closed Loop problem.

If my check engine light comes on again, is there a way to pull the code without shutting the engine off? I'm afraid if I turn it off, then try to pull the code, it won't give one.

Thomas.

 

Now I have just gotten my third gen firebird so I haven't had a chance to look it over yet. To see how these engines differ from cars I've had in the past. As far as your problem goes I think I may have a solution. On an 89 Daytona that I had it was doing the exact same thing. After trying a number of things I decided to try the EGR valve. This is where I'm not sure if the engines have one. I believe they do because it's an emissions thing. Anyway, find your EGR valve and with the car off reach inside the housing and push on the diaphragm with your fingers. Does it move freely? If not, replace the EGR valve. If so, next step. When your engine is cold touch the diaphragm and not the position in the housing. Next start your car and let it get to normal operating temp. Now reach inside and touch the diaphragm. Has the diaphragm moved? If so, your EGR valve is fine. If not, check the vaccum hose going into it. I believe they are vaccum operated. Check to make sure there is a vaccum both when the car cold and hot. With these tests you should be able to detemine weather or not it's the EGR valve. Let me know how it goes.

 

Well we decided to test the fuel presure and came up with a wopping 4 pounds. So my problem turns out the be the fuel pump.

 

TPS. I've had mine replaced once, and it's screwed up again. Do you think that Chevy will pay for the new one since they put a shafty one on in the first place?

 

This could just be coincidence, but I filled my car up with gas yesterday morning and the problem has not happened since.

My check engine light was coming on 1-2 times a day, and when it did, the car would run very sluggish. I could turn it off, then start it back up, and it would run fine again until the light came back on.

Well, yesterday morning I filled it up with 93 octane and have driven about 100 miles so far with no problems.

Does this mean I might have a fuel pressure problem? .... a pump or a clogged filter? ...... Or is this just coincidence??

Thomas.

 

Replaced it, coil, wires, everything... I've tried three distro's... No luck

 

HEY STOOP~!!!
i have the sammme problem, youd be driving along, then something would just lag, light comes up, you punch it and theres no power?
WTF is that. its not the relay, i replaced.
not filter, was replaced, will clean whole fuel sys soon, but i doubt thats it as well.

i think its the fuel pump, what do you guys recomend for a new pump??
and how much.
THANX!!!

------------------
91 FireBird 305 V-8
Edelbrock Catback,
ghetto rigged cold air intake,
"My G/f Once Wanted To Break Up Because Of Competition With The Car."
GheTTo Riggers INC.
We Make Mcgyver look Like Crap

 

Yea, that sounds like the problem I'm having. I don't think it's the fuel pump anymore though. I have a fuel pressure gauge under the hood, and it stays very constant right at 13lbs.

The problem has developed and gotten worse. I think I'm dealing with an electrical problem now.

I posted a new thread in the Electrical board, and you can view it Here

Lets hope someone can figure this thing out, it sucks having to worry about my car dying while I'm driving around!

Thomas.

UPDATE: The car dying problem turned out to be a faulty wire from the distro block to the starter. I dunno if this would cause my surging problem (I don't think so) but we'll see what happens when I replace the faulty wire.



[This message has been edited by Stoopalini (edited June 15, 2001).]

 

Did anyone figure this out yet? I replaced that wire and it runs again, but I still have the slight surging problem.

The car is also doing the stalling bit when I stab at the gas pedal.

Could a faulty O2 sensor cause this problem? I was wondering: if the O2 sensor is bad, and the ECM is getting invalid info, that maybe it could cause the engine to surge??

Thomas.

 

Has anybody checked their base timing? If it's too far advanced you will notice that it is harder to start and sometimes too much base timing will cause knock with lower octane gas and then the knock sensor will retard timing a LOT to get rid of the detonation. When the timing is retarded you will notice NO power. Next I would watch the injectors by keeping the car at idle and just flipping the TPS sensor. You should see a bunch of fuel injected into the TB instantly and the engine should stumble. If it doesn't and it actually likes the extra gas then it sounds like your fuel pressure.
The MAP sensor is Manifold Air Pressure.
The MAP sensor usually doens't go bad. I've only seen one go bad so far. If a bad sensor you will see an SES light. Anybody pull any codes from their ecm yet? They don't go away until you disconnect the battery.
Definatly check timing. When spark wires go bad you will have a terrible ride. The distrib will arc and you'll get nasty acceloration all the time.

------------------
, Jon (350 TBI!)
91 Red My website

 

I finally pulled the codes last night and only one code is present -- "44" which is a lean condition reported by the O2 sensor circuit.

I plan to trace down the O2 sensor wire and see if it is grounded out somehow (header maybe). If not, I'll replace it since I originally thought the O2 sensor anyway.

Just thought I'd give an update,

Thomas.

 

thats not it stoop, i forgot the number when i pulled it last.
but i can tell it like this,
you would be driving, and normal acceleration then as "the pressure would build" the fuel pump loses and cant keep up with that. so it drops down to "4" and when you slam it, "6" so it would still run like sluggish, ive replaced the fuel pump relay, and no affect, i run premium allllll the time. this is fuel related, im pretty sure, thats my best guess.
im not sure, but i think the trouble was 32, or 34. i cant remember.
oh well, all ive come up with is, put car in neutral when driving, turn off, three seconds, back on and keep going, and the only way to Not throw it, is to be punching it all the time.
and also, when the car has most power is when its just started and cold, And The gas pedal is more firm. ? why is that. when it runs like crap its loose.
oh well, keep the info comming guys,

 

Well, I traced down the wires and found that the Air/Fuel mixture gauge I have is connected directly to the O2 sensor's wire. So I disconnected the gauge.

I've only been about 30 miles since I disconnected it, but I didn't have any problems at all. It's running so much better!

It seems the Air/Fuel mixture gauge wires are in need of replacement. Maybe the signal wire is grounding out somewhere, or the ground just isn't good enough? I plan on rewiring the gauge all-together to resolve it.

So, for anyone still having this problem, I would recommend checking the O2 sensor wire and make sure it's not grounding out anywhere.

Thomas.

 

I don't know about mine surging like stated above, but when I start my car up cold, the idle fluctuates anywhere from 300rpm to about 1k. I replaced the IAC with a brand new unit a few days ago and it seemed to have helped it some, but I'm still unsure. (I think I posted this elsewhere a while back, but this seems like the appropriate category..)

------------------
1992 25th Anniversary Ed. Camaro RS

 

My car ALSO has ben doing this. I have changed the plugs, wires, cap, rotor, and fuel pump. It surges like a beast at idle and I have a miss around 3 grand. It only does it when it is above 160 or so and I cannot for the life of me figure it out. My mechanic told me that it may be a bad pick up in the dist. I have been running it on the drag strip here like it is and I still picked up almost 4 tenths in the 1/8th!! I love this holly fuel pump. Even missing, I am still beating the guys that I could never even touch before! If anyone figures theirs out please e-mail me or if I figure it out I will do the same for you!

Eric

------------------
Teal 1991 Camaro R.S., T-Tops,
Leather, Re-worked 700r4 also w/kit,
MSD ignition, MSD 8.5 mm. superconductor wires,
MSD Coil, ADS superchip, Open element air cleaner,
K-n-N filter, Gutted cat, Flowmaster cat-back system,
Edelbrock TES headers, March 3piece billet underdrive pulleys
3.73 gears
http://www.geocities.com/gitarz2/camaro.html
I was shocked to see that companies sold a taillight
set for a rustang! Since when do they have taillights????

 

I replaced all of the vacuum hoses on my RS today, and so far my surging seems to be fixed. The PCV hose had rotted and had a big hole in the bottom, and one of small hard plastic hoses going to the heater controls had been rubbing on a hose clamp and had worn a hole in it. I'm actually kinda embarrassed that it was such an elementary problem!! It just goes to show, that when there is a problem with an EFI car, too many people (me included) jump to the conclusion that "it must be a sensor" or "something's wrong with my computer" but a vacuum leak on the most futuristic, ellaborate, EFI set-up in the world is going to have the the same effect as it would on a 50 year carb.!! This would have been the first thing I would have checked on a carbed car, but I don't have a clue why I didn't check it on my RS sooner. Anyway, my problem is fixed as far as I can tell, and naturally, the car runs so much better now than it did this morning on the way to parts store to get the hoses. If everyone hasn't replaced the vacuum hoses that have posted on the topic, it would definetly be worth a look!!

------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing



[This message has been edited by Basett_Racing (edited June 24, 2001).]