Engine Problem
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
Engine Problem
Well, I'm at a loss now! I will admit defeat and look to this forum for some help. Hope someone can at least diagnosis the problem. I have looked at a few local shops for help and most are not willing to troubleshoot for whatever reason. Dont want to send it back to Chevy!
1988 stock motor L-98, is missing, constant and get worse as motor gets warm. I have administered the following meds and checked the following pulse rates: New plugs and wires, checked the FP-good at 40#and held for @20min, checked all the injectors, and inj harness' all good, checked timing, good set at 6*BTDC
I had to also replace the exhaust from the minifolds including new converter due to pluggage. Sounds much better except for the constant miss. What am I missing? any suggestions will be very thankful.
1988 stock motor L-98, is missing, constant and get worse as motor gets warm. I have administered the following meds and checked the following pulse rates: New plugs and wires, checked the FP-good at 40#and held for @20min, checked all the injectors, and inj harness' all good, checked timing, good set at 6*BTDC
I had to also replace the exhaust from the minifolds including new converter due to pluggage. Sounds much better except for the constant miss. What am I missing? any suggestions will be very thankful.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
"checked the injectors" How did you do that? Cold,Hot? Both? NOID light? Codes? Can you isolate the miss to a cylinder(s) or is it random? Isolate to a bank? Obviously my knee jerk reaction is a problem in the fuel system.
Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
have you noticed the engine coolant temp abnormal? or a rich exhaust, or tail pipes black? unplugged the MAF to look for a reaction? when unplugged, the ecm uses other values -maybe from the TPS- to determine fuel delivery signals. but it uses other values from various sensors, including the CTS.
can also unplug TPS -not at the same time as other sensors- but not sure about the CTS. what you want is a reaction while the sensor is out of the circuit.
as muffin said, should show a code if it is sensor related. if you have fsm, there are many pages, "symptoms" that guide you.
*** may not be high probablilty, but you can remove vac line to FP reg to check for fuel in the line -in case you see evidence of rich exhaust, from plugs, whatever. the deal is that it can be ignition, fuel, even things you have changed, spark lks, etc..
can also unplug TPS -not at the same time as other sensors- but not sure about the CTS. what you want is a reaction while the sensor is out of the circuit.
as muffin said, should show a code if it is sensor related. if you have fsm, there are many pages, "symptoms" that guide you.
*** may not be high probablilty, but you can remove vac line to FP reg to check for fuel in the line -in case you see evidence of rich exhaust, from plugs, whatever. the deal is that it can be ignition, fuel, even things you have changed, spark lks, etc..
Last edited by joe paco; Sep 22, 2011 at 09:44 AM. Reason: add***
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
I am limited on the code reader. Have the dime store model, spitting out code 12, the only code its ever spit out! I have not pulled valve covers or checked compression yet, hoping to not go there YET!
I also do not have the service manual for this car.
Some History:
Previous owner had replaced FI, Mufflers, brakes.
Car was purchased last month and was running good. After a few days of ownership, the skip developed. So I started with the plugs/wires, fuel filter, air filter, figuring it just needed a little tune up. nothing helped.
I also do not have the service manual for this car.
Some History:
Previous owner had replaced FI, Mufflers, brakes.
Car was purchased last month and was running good. After a few days of ownership, the skip developed. So I started with the plugs/wires, fuel filter, air filter, figuring it just needed a little tune up. nothing helped.
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
Whan I checked the FP, it comes up to @40# and it held there for @20min before starting to leak off. After an hr it ws down to #10 or so. Also took if for a spin with FP gauge on winshield so I could monitor, and FP stayed @35-36# at WOT. I would drop off to @22-24# when letting off the throttle.
I also checked the injectors cold first then somewhat hot after the FP check. The engine is not running hot, gauge showing @155-165*.
Tail pipes are clean, no smoke coming out exhaust. the old plugs did look a little white on tips to me. So I thought it might be running a little lean!
What type of code reader should I get and where to get it? The one I have is a Actron from Adv Auto.
Thanks to all for the help.
I also checked the injectors cold first then somewhat hot after the FP check. The engine is not running hot, gauge showing @155-165*.
Tail pipes are clean, no smoke coming out exhaust. the old plugs did look a little white on tips to me. So I thought it might be running a little lean!
What type of code reader should I get and where to get it? The one I have is a Actron from Adv Auto.
Thanks to all for the help.
Last edited by basshooked; Sep 22, 2011 at 10:15 AM. Reason: added info
Race Director
Joined: Sep 2003
Posts: 16,839
Likes: 341
From: Database Error Indiana
Odds are, you have no codes. Code 12 means the ECM is working. Another code reader will just tell you the same thing. If you have a laptop a scan program will get you good information. A dead miss has to be ignition or compression related since you have ruled out injectors. Maybe pull one plug wire at a time and isolate the miss to one cylinder ???
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Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
Whan I checked the FP, it comes up to @40# and it held there for @20min before starting to leak off. After an hr it ws down to #10 or so. Also took if for a spin with FP gauge on winshield so I could monitor, and FP stayed @35-36# at WOT. I would drop off to @22-24# when letting off the throttle.
I also checked the injectors cold first then somewhat hot after the FP check. The engine is not running hot, gauge showing @155-165*.
Tail pipes are clean, no smoke coming out exhaust. the old plugs did look a little white on tips to me. So I thought it might be running a little lean!
What type of code reader should I get and where to get it? The one I have is a Actron from Adv Auto.
Thanks to all for the help.
I also checked the injectors cold first then somewhat hot after the FP check. The engine is not running hot, gauge showing @155-165*.
Tail pipes are clean, no smoke coming out exhaust. the old plugs did look a little white on tips to me. So I thought it might be running a little lean!
What type of code reader should I get and where to get it? The one I have is a Actron from Adv Auto.
Thanks to all for the help.
you can verify that codes are being set by creating one. unplug TPS, start, then check for a code 21, I think. checking the sensors mentioned is free, nothing lost but time.
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
No, I havent checked the cap and rotor. Dont even know why I havent checked it yet. I will check it later today. I have burned 2-3 tanks of gas through it all from the same Hess station. I use it exclusively when I can and have had no problems in other toys/vehicals. Thanks again for everyone's help. I will post later today what I find with the cap and rotor. Hope thats it! Everyone cross fingers, I'll hold my breath!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Really aren't any codes for a miss on an '88.
You need to determine if it's random or isolated to a single cylinder. Get yourself some 1/4 inch vacuum hose and cut it into 2 inch pieces. Remove each plug wire at the Distributor and insert one piece of your cut hose over the plug tower and insert the other end of the plug wire into the hose. Start it up and kill each cylinder by touching it with a grounded test light while observing a tach. The cylinder that doesn't drop - or drop as much as all the rest - is causing the problem.
You need to determine if it's random or isolated to a single cylinder. Get yourself some 1/4 inch vacuum hose and cut it into 2 inch pieces. Remove each plug wire at the Distributor and insert one piece of your cut hose over the plug tower and insert the other end of the plug wire into the hose. Start it up and kill each cylinder by touching it with a grounded test light while observing a tach. The cylinder that doesn't drop - or drop as much as all the rest - is causing the problem.
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
Really aren't any codes for a miss on an '88.
You need to determine if it's random or isolated to a single cylinder. Get yourself some 1/4 inch vacuum hose and cut it into 2 inch pieces. Remove each plug wire at the Distributor and insert one piece of your cut hose over the plug tower and insert the other end of the plug wire into the hose. Start it up and kill each cylinder by touching it with a grounded test light while observing a tach. The cylinder that doesn't drop - or drop as much as all the rest - is causing the problem.
You need to determine if it's random or isolated to a single cylinder. Get yourself some 1/4 inch vacuum hose and cut it into 2 inch pieces. Remove each plug wire at the Distributor and insert one piece of your cut hose over the plug tower and insert the other end of the plug wire into the hose. Start it up and kill each cylinder by touching it with a grounded test light while observing a tach. The cylinder that doesn't drop - or drop as much as all the rest - is causing the problem.
Never seen this procedure done with the vac hose before. What kind of test light do I need? I have the reg 12v idiot test light. Will that work? Am I putting the rubber tubing over all or doing one at a time? I would like to try it but not completely sure how. Is there a video on You-tube or something I could watch it being done?
I believe the miss is random. but not 100% sure. all the old plugs looked pretty much the same when changing. I will perform a compression test later as work calls for my presence for the next 8 days.Thanks for the help and I will keep all that have helped up to speed.
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
Talked to a guy today that has a scanner. He said it would pull any codes and scan several parameters on the engine. He is actually a tranny mech, but he seem to know alot about this motor and the LT-1. Supposed to stop by tomorrow night after work and let him scan it to see if we can find out anything. If that does not work, guess I will try the vac hose and the test light.. Thanks again guys for all the help! Maybe some day I can repay you all in some way. Who likes to fish?
Instructor
Joined: Jun 2011
Posts: 182
Likes: 0
From: Bowling Green Ky
is the engine fully warmed up, still running 155* F? seems low to me, for a normal c4. if the CTS is reading low in error, it can affect the a/f ratio. even in closed loop, so fsm says. would make it richer, in this case, I think.
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 17
Likes: 0
From: Tax State USA NY
What should the normal operating temp be at? Is this the wrong thermostat? How can I check the temp to verify its accuate with gauge on dash board? Hopefully tonight when we get the scanner hooked up it will tell me something that I am overlooking. Thanks!
Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
What I'm reading is the coolant temp on the digital dash gauge. It appears to be working correctly. It looks like the thermostat is opening at @160* and temp drops back down a bit and stays fairly stable between the 155 to 165 temp. I have never seen this temp above the 165 mark and lower than the 150 mark after engine warms up. Since I.ve owned the car, its never overheated and all indications that I see, the cooling system is working OK. ie: thermostat, cooling fan etc. I dont have the service manual yet, so not sure what temp should be!
What should the normal operating temp be at? Is this the wrong thermostat? How can I check the temp to verify its accuate with gauge on dash board? Hopefully tonight when we get the scanner hooked up it will tell me something that I am overlooking. Thanks!
What should the normal operating temp be at? Is this the wrong thermostat? How can I check the temp to verify its accuate with gauge on dash board? Hopefully tonight when we get the scanner hooked up it will tell me something that I am overlooking. Thanks!
the concern is that if the temp is 230, example, and the temp gage is 155, the ecm would adjust fuel for the 155. Or, cts is not normal in its signals. its supposed to be in "Closed" loop at 104*, so says my fsm, so it may not matter. using signals from 02 sensors.
the high temp stat is for emissions control, but that is a huge part of the whole system.
may not be related to your issue, just looking for clues. you might consider a higher stat for winter.
