Dan87IROC-Z

Okay, here we go again. My car chugs and stumbles through the operating range. It seems to be the worst when I am going up hills. Under full throttle there is a popping sound comming from under the hood. And there is a serious lack of power.

I just replaced the cap, rotor, and coil. I just adjusted the TPS and cleaned my K&Ns. The plugs and wires are all in good shape and less than a year old. I have also in the past year and a half replaced the ECM, MAF, battery, alternator and starter. Its throwing no codes and there are no weird smells or anything other than what I described above.

Any Ideas?

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET : 14.32 @ 97.7mph
(corrected for elevation)

Next on the list: LT4 HOT Cam

evilho7810

Have you checked your timing?

El Guapo

lm thinking cross/miss firing. Easiest way to check is to replace the wires. However, you can run a plastic handled screwdriver along the sides of wires. You will see a spark from wire to screwdriver if there is a cut or burnt spot on the wires. lf so, you have just found the problem.

Also, you didnt say that you actually checked your plugs. Doing this would show if one isnt firing. Although you probably did check, just thought l'd through that out there.

Clayton

RB83L69

That sounds like either an ignition related problem, or a blown head gasket.

You say you believe all the ignition components themselves are good; check to be certain the plug wires are in the correct places on the cap. If all that is right, do a compression test.

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"So many Mustangs, so little time..."

Ski89Z28

I agree with RB83L69 but I would try replacing the ignition control module in the diatributor. you replaced everything else so finish it with that.
Just my .02

Good Luck!

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89 IROC 350 Auto
Custom DUAL Exhaust
Edelbrock Performer 6085 Aluminum Heads
ZZ9 Cam
TPIS Level 5 Chip
14.01 @ 97.0mph with 2.77's gears and a bad ignition control module!
And Free mods.

Dan87IROC-Z

Well, if it was a blown head gasket, wouldn't it be leaking oil or antifreeze?? It may be ignition, I can check my wires and plugs again I suppose.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET : 14.32 @ 97.7mph
(corrected for elevation)

Next on the list: LT4 HOT Cam

John'89L98

Did the problem come after replacing your your cap? If yes, check to make sure you have them in the right order. If no, try replacing your fuel filter. - John '89 L98

Pony Killer

Does the timing mark move around alot on the ballancer when you check the base timing, with the engine at a steady speed?

ifit does, your timing chain is worn out,

when you load the engine up, the cam and ignition timing will retard, and when you unload it, the cam and ignition timing will advance.


It's just a guess.


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It's always SOMETHING
"Sounds like Barry White at idle, Teddy Pendegrass wide open..
if it don't sound like Micheal Bolton your alright"

JakeJr

Dan, your situation is one of those that can be realtively simple to correct or a real PIA. You're going to need a service manual that has a good trouble-shooting section inorder to fully diagnose the cause, but here are some tips on some of the things you can do even without one.

Without specialized diagnostic equipment, it will be simply a process of elimination to discover the cause.

I feel there are two main areas that need to be looked at; ignition and fuel. Of course it could be something like a bad 02 sensor, or Manifold Air Temp sensor, etc., but I'd first zero in on ignition, then fuel. If a sensor is bad, the ECM should throw a code.

First, pull all the plugs and check them for proper gap and look closely at the porcelean for cracks. Check the color too, it should be very light tan. Look for anything unusual like tiny specs or rounded electrode which would indicate detonation or improper timing.

Next check that all the wires are giving good spark and that none are arching over to metal. Check that they are properly routed; that no wire is on the wrong plug (crossed). It's amazing how well a TPI engine will idle with a couple of plug wires crossed; the miss is sometimes barely noticable, but it'll show up in throttle response.

Check the terminals inside the distributor cap for corrosion and use fine sand paper to clean them. Check the rotor tip and clean it too with the sand paper. Look for ang sign of carbon tracking inside the cap which would mean a possible crack in the cap.

A digital voltmeter and a service manual will be needed to check the coil and pickup for proper resistance.

Put a vacuum gauge on the engine at idle and see if the idle reading is constant without and sudden dips. Dips would indicate a vacuum leak somewhere. If you see any dips, get a can of spray injector cleaner and spray around all the sealing surfaces. If the idle jumps or falls when spray is directed at a particular spot, you've found your leak source. Check where the injectors enter the manifold too; this is an oftem over-looked source of a vacuum leak.

Disconnect the Timing connector (engine off) and with the engine idling, check you initial timing setting. Rev the engine slightly and see if the timing moves. You should be able to get about 22 degrees of timing even with the ECM not contributing to ignition timing.

Remove the module and take it to your local auto parts store for testing. A lot of stores have module test equipment and will test your module for free. If it checks okay, make sure you use new dielectric grease under the module when you reinstall it; remove all of the old grease first.

Reconnect the timing connector, disconnect the battery for at least 30 seconds to clear the error code that was set when the ECM detected the engine running with the timing connector disconnected and start the engine.

Let it enter closed loop. Here a Diacom or Scantool is needed to make sure that your 02 readings are normal. Readings should cross 450mv repeatedly and should range from about 100 mnv to about 800/900 mv. Lean/rich mixture reading should constantly cycle between lean and rich. Rev the engine and thetiming should move as rpms increase.

Check your IAC counts which should be 25 or less at idle and should change up and down slightly as the ECM maintains the commanded idle speed.

Use the digital volt meter to check the TPS setting and also check that the voltage readings increase at a smooth and steady rate when you open the throttle by hand. Of course this is done with the engine off/ ignition on. Any skips or jumps indicates a faulty TPS.

Connect your timing light to each plug wire as close to the plug as you can get it and rev the engine while watching the flashing of the timing light. The flashing should be steady and increase in frequency as the revs increase. Any sudden or intermittent non-flash indicates that no spark was being sent to the plug.

Fuel checking involved checking pressure at idle with the vacuum line disconnected; changing the fuel filter, installing a fuel pressure gauge and watching to see if the pressure holds when the engine is shut down.

Once you get to the point of check fuel pressure, you'll need a gauge that can be mounted to the fuel rail and that has a long hose which can be taped to the windshield. Drive the car and watch the fuel pressure. Try to duplicate the conditions underwhich the malfunction occurs and see if the fuel pressure is holding at that point.

There are some additional things that you can check, but this should keep you busy for a while. At some point you'll find the cause. You may hit it right off the bat or it may be the last thing you check; there's really no way to know for sure.

Of course, any of the things I've listed that you have already checked can be scratched off the list.

I hope some others will chime in with additional suggestions.

Hope this helps. Keep us posted.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9


[This message has been edited by JakeJr (edited January 03, 2001).]

RB83L69

A blown head gasket does not necessarily leak water or oil. I had one myself recently in my own car, where it blew between cylinders #5 & #7. Look at the firing order and you will notice that 5 fires when the 7 intake valve is open; so every #5 firing lit off #7 too by way of the path between them, which of course popped back through the intake. A burned intake valve will cause a similar behavior, since each time that cylinder fires, flame will shoot out of the leak and set the whole charge in the intake on fire.

Again, a compression test will tell the tale. Do as others have suggested, check your fuel pressure and all that; but add a compresssion test to your list of diagnostic steps. You might be able to "rent" one at Auto Zone or Kragen or somewhere, which is a whole lot cheaper than replacing anything, even one spark plug. Your problem doesn't sound like you're going to get anywhere by parts swapping.

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"So many Mustangs, so little time..."

Dan87IROC-Z

I just replaced the cap, rotor and coil and the car was acting the same way before the swap. The fuel pump and fuel filter are new. I ran some of that cheap STP fuel system treatment through the car just before it started acting up, could that have caused it? I usually use the premium GB44K treatment, but my dad said the STP stuff worked on his car so I bought some, its like $20 less.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET : 14.32 @ 97.7mph
(corrected for elevation)

Next on the list: LT4 HOT Cam

MEANGREEN

I don't know and haven't seen your ride, but if you have a stock catalytic converter, it may be clogged, especially since you're saying a lot of this is going up hills, etc. An easy check other than gutting that POS would be to pull your O2 sensors and look for black deposits and the smell of fuel, general rich conditions. If this is what you find, than either that cat is clogged, or your sensors are bad. Hope you find the problem and hope it's cheap. It could always be an electrical gremlin, but for some reason, this sounds all too familiar. Same thing happened to me, and because of a previous electrical problem, it clogged my cat, blew my gaskets eventually, and now I'm still fixing things because of this, exact same symptoms as you described.



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Dan Young
1995 Z28/M6
Groton, CT

1985 Z28/A4
(Prospective purchase)

slopoke

check the reluctor coil inside the distributor. I had same problem 6 years ago.

Michelob

I recently had a similar problem with an 87 L98. It appeared to be idling ok( by the tach ), but the motor was shaking around and sounded weak. Also when driving it was chugging badly and way down on power. At higher rpm the motor smoothed out somewhat but still was way down on power. The problem turned out to be crossed plug wires. It took a while to find because it was idling too damn good to consider it was down 2 cylinders.

burnoutrpm

im with the other 2 guys who posted responses check the cat and the module and also the timing.

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods 400 performer rpm intake (polished) and 600 edlebrock carb, comp roller cam, and way better heads. orpossibly a 383 stroker?

Dan87IROC-Z

Thanks a lot guys. The plug wires seem to be in good shape. I have to take a look at the plugs themselves still. I am also going to pull my O2 sensor and look at that when I gut the cat this week.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: LT4 Hot Cam, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Gutted Catalytic Converter, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, Fully Ported TPI Plenum and Base, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

custman87T/A

I had the same problem about 2 months ago and I couldn't figure it out worth a s**t. Spitting and sputtering with no codes. I wound up starting the car after I cooled off and heard a slight clicking sound along with the sputter which was happening at idol through all ranges especially uphill and it turned out to be that my diverter valve off the air pump was stuck...alittle throttle body cleaner sprayed through the hoses cured it...will it work for you I can't say but it sounds like the identical problem.

monte_man_79

Guys...... The camshaft is shot!
I have had one go out before, and they describe the symtoms perfectly! Popping though the carb (or TB) under load or under throttle. And lack of power. Take one of the valve covers off start the moter and see if ALL the rockers are moving equally! You may find that one or two or three are moving very little, or not at all! And that means a bad cam! BTW, how many miles are on this car?

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280hp LG3 305 in 79 monte carlo
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May the gas flow free and the lights be green.

Dan87IROC-Z

The car has just over 90,000 on it. I did just buy a new cam and I am waiting for it to arrive to install it, so if thats the problem, then its going to be fixed.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: LT4 Hot Cam, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Gutted Catalytic Converter, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, Fully Ported TPI Plenum and Base, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)