1988 Jeep Cherokee Over Heated the engine

Tiny
LONESTAR5966
  • MEMBER
  • 1988 JEEP CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 28,000 MILES
Blew a radiator hose bottom one kept driveing it till made it home have a hurt foot chip fracture to far to walk to get new hose anyway now I have a problem with the no. 1 cylinder either a bent valve or cracked piston anyone else have this problem and what was damaged kinda misses right off idle then kicks in number one spark plug dirty black and white all others spark plugs fine oil looks good just had changed it doesnt over heat now so I think head and gasket ok thanks for any feedback on this one


http://www.2carpros.com/forum/automotive_pictures/203409_041908_1802_2.jpg

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Wednesday, June 18th, 2008 AT 7:33 PM

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Tiny
RASMATAZ
  • MEMBER
Now I have a problem with the no. 1 cylinder either a bent valve or cracked piston

How do you know this-did you actually do a compression check? No. 1 plug dirty black could mean an injector problem

doesnt over heat now so I think head and gasket ok thanks for any feedback on this

If there's a problem with the head and gasket it will overheat
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Wednesday, June 18th, 2008 AT 7:41 PM
Tiny
LONESTAR5966
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How do you know this-did you actually do a compression check? No. 1 plug dirty black could mean an injector problem

Compression check Not yet it only happened day before yesterday haven't seen my compression checking equipment in a while did disconnect injector and ran rougher smoothed out when reconnected
Either could affect compression
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Wednesday, June 18th, 2008 AT 8:06 PM
Tiny
LONESTAR5966
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Thanks

Are We Through Picking At My Short comings !

How About Getting Off Your High Horse And Down To Business

Does the 88 Jeep 4.0 Renix Engine Have A History Of Any Common Problems Such As Bent Or Stuck Or Sticking Valves Cracked Pistons After A Over Heating Problem Please Keep In Mind That This Engine Has Over 280,000 Miles On It I Thought This Would Be A Good Place To Ask Such A Question Thanks
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Wednesday, June 18th, 2008 AT 9:33 PM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
Nobody is picking on you and I am not making fun of you. I appologize if I was condescending and sorry about the part of irritation; I did not read the conversation correctly. Please understand your fragmented sentences make it impossible to make out what you are trying to say.

Blew a radiator hose bottom one kept driveing it till made it home have a hurt foot chip fracture to far to walk to get new hose anyway now I have a problem with the no. 1 cylinder either a bent valve or cracked piston anyone else have this problem and what was damaged kinda misses right off idle then kicks in number one spark plug dirty black and white all others spark plugs fine oil looks good just had changed it doesnt over heat now so I think head and gasket ok thanks for any feedback on this

Its not hard, just separate your subjects so I can make heads and tails of the problem.

"Either could affect compression"
Now I have no idea whether you are refering to the fact that a bent valve or cracked piston would EFFECT compression; or that you are stating that unplugging and plugging in your fuel injector is effecting your compression. One is correct and the other is not so I am sorry if I couldn't understand which of these you were refering to.

"Does the 88 Jeep 4.0 Renix Engine Have A History Of Any Common Problems Such As Bent Or Stuck Or Sticking Valves Cracked Pistons After A Over Heating Problem Please Keep In Mind That This Engine Has Over 280,000 Miles On It"

Sticking and bent valves are two totally different things. Sticking valves is very common and happens to all aged engines. No the AMC 242 is very well designed and has served Jeep from the mid 80's through the early 21st century. As stated below bent valves or cracked pistons are indicative of detonation or extreme wear. Running a car with no coolant will no doubt give the engine the possibility of potentially warping, cracking and destroying internal components. (I am not sure if the 3.8L is just the 4.0L with a slightly shortened stroke)

Bent valves and cracked pistons are not a part of normal wear and tear on an engine. That would indicate detonation or an extreme misalignment in your timing chain.

280,000 miles on an engine would be indicative of extreme wear. Have you ever overhauled the engine?

So is there a bent valve/cracked piston?
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Wednesday, June 18th, 2008 AT 10:59 PM
Tiny
LONESTAR5966
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Wont Know Till I Take It Apart Just Wondering About The History Of Engine Hoping For Some Direction Got My Punctuation Criticized Accused Of Attacking Someone Not Much Help From Mechanical Standpoint Lot Of Personal Biases Contradicting Information
Just Try Reading It Through Without Your Punctuation It Should Come Naturally
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Wednesday, June 18th, 2008 AT 11:58 PM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
What bias or contradictory information?
What twisted context?

Look forget it what is wrong with your car right now at the moment.
Is it misfiring, overheating or is there nothing wrong?

Overheating will almost always result in pre-ignition or detonation.

280,000 miles is extreme so unless you have used synthetics then you have wear. Oil pressure reflects the condition of your main bearings which does not include the condition of your cylinder bores, pistons, camshaft or valvetrain. On a well balanced crankshaft main bearings can last upwards of 200,000 miles as long as there are no abrasives in the oil.
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Thursday, June 19th, 2008 AT 12:52 AM
Tiny
LONESTAR5966
  • MEMBER
Kinda misses right off idle then kicks in. Number one spark plug dirty black and white "Lightly Coated " All others spark plugs fine. Oil looks good just had changed it. Doesn't over heat now so I think head and gasket OK. Thanks for any feedback on this !
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Thursday, June 19th, 2008 AT 1:04 AM
Tiny
LONESTAR5966
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If a valve spring fails how does engine react
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Thursday, June 19th, 2008 AT 1:14 AM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
Have you checked the distributor and the timing? I can't remember if it is adjustable or not, but check the terminals on the cap for corrosion or excessive burn marks. Make sure the rotor is ok as well. Are the resistance values for the plug wires acceptable? It should be 4,000 ohms per foot. Let me know the results of that.
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Thursday, June 19th, 2008 AT 1:16 AM
Tiny
LONESTAR5966
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Well maintained all recently replaced. Checked timing and set.
If valve spring fails how would that affect engine performance was running perfectly daily driver
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Thursday, June 19th, 2008 AT 1:32 AM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
The valve will not completely close resulting in a loss of compression. Depending on which valve the engine may backfire through the intake manifold or release unburned fuel into the exhaust stream causing afterfire (which is what most people know as backfire). Remove the valve cover and perform a leak-down test on that particular valve to verify the spring tension.
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Thursday, June 19th, 2008 AT 1:36 AM
Tiny
LONESTAR5966
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Just the opposite loss of power off idle then picks-up rougher idle lower rpm's around 500 usually give or take 100 rpm's
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Thursday, June 19th, 2008 AT 1:42 AM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
So the misfire is more pronounced off idle or at idle? If it is misfiring off idle or under acceleration then the problem is in the distributor centrifuge or vacuum advance (if there is a vacuum advance) or possibly slack in the timing chain. If the misfire is more pronounced at idle and disappears under acceleration or higher rpms then the mixture isn't right (it dosen't have the weber carb does it? Its TBI?), The timing is slightly off, or possibly a sticking or not closing valve, as you stated. There are alot of possibilities for it to misfire at idle.

Start with a compression check on that cylinder to verify the integrity.
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Thursday, June 19th, 2008 AT 2:20 AM
Tiny
LONESTAR5966
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Will do
Thank you for your time and attention to this matter will let you know till next time have a good one and keep on keepen on from lonestar5966
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Thursday, June 19th, 2008 AT 2:44 AM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
I have a Wrangler with Renix ignition system and the MFI fuel system only mine is the 2.5L instead. Have you reset your MAP sensor because once I had a problem with a misfire/rough idle and had to have the MAP sensor "reset". The PCM has a basic diagnostics system for drivability. Key On-Off the ignition 3 times and then on the 3rd let the ignition remain on. The computer will flash the code(s) through the check engine light. The check engine light will immeadiatly start with the first trouble code. Count the number of flashes then when the light pauses for 2-3 seconds then write that number down. The PCM will then display a second set of flashes. Count them and write that down. Each code will come in 2 digit cycles. The code 55 (5 flashes, 2-3 second pause, 5 more flashes) will signal the end of the diagnostic trouble codes. I have a manual for all the trouble codes displayed so if you recieve anything other than 55 let me know.

And that comment about oil pressure I made, I can vouch for that because I have 30-50 psi of pump pressure and have never changed the main bearings. I have rebuilt the engine to extremely tight tolerances which has given me such good oil pressure. I uncapped one awhile back and it had significant wear on the babbit; however, I figured I could wait. I am about to fix a rear main so I wanted to do it all at once.
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Thursday, June 19th, 2008 AT 3:56 AM
Tiny
LONESTAR5966
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Are you talking about the 2.8 V6 or is that the 4 cylinder?

I Have a 2.8 V6 in my camaro manual 5 speed apparently they came in some jeep products
Also a 2.0 4 cylinder in a Chrysler Le baron with a cracked piston in the no. 1 cylinder around 200,000 miles on it
Those 4 bangers need a lot of maintenance every 100,000 miles or so

Tried to do compression check taday couldnt find the right fitting seemed to hold compression at tdc and valves opened and closed leaning towards new timeing chain
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Thursday, June 19th, 2008 AT 9:45 PM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
So you don't have the onboard diagnostics?

I changed my ring gap to 10 thousandths of an inch
Polydyne coating on piston heads, ringland and skirt.
A high performance cam from Quadratec
MSD capacitive discharge ignition
About to turbocharge it.
Along with k&n, bosch plugs and some other refinements
I am guessing right now it has about 30+ hp over stock but not real sure (never had it dynoed)

Ah so thats the car with the cracked piston. Ok.

Actually I have found that the engine is extremely durable and has had nothing in the way of problems. The only thing that is annoying is valvetrain chatter which I think is caused mostly by the crappy stamped rocker arms. I want to invest in the yella-terra rocker arm assembly but I can live without. Not like you can hear it hardly anyway with the glasspack.
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Friday, June 20th, 2008 AT 12:37 AM
Tiny
LONESTAR5966
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Friday, June 20th, 2008 AT 11:45 AM
Tiny
AIRSOFTSOLDRECN9
  • MEMBER
That is strange, I was positive all the jeeps 1988- 1995 had the ignition key type diagnostics along with OBD I.

150 cu in. 2.5L
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Friday, June 20th, 2008 AT 12:25 PM
Tiny
LONESTAR5966
  • MEMBER
The first 4.0 engines in 1987 had RENIX (Renault/Bendix) engine control systems, which were quite advanced for their time, but are now handicapped because there are very few scan tools which can be "plugged in" to a RENIX system for diagnosis. The Renix also used a engine knocking sensor, which allowed the computer to know if detonation was occurring, thus allowing the computer to make the appropriate changes to prevent this. Renix systems have no "permanent" memory for the diagnostics system. Once the ignition switch is turned off any codes generated are lost, thus making it difficult to detect intermittent problems.

http://en.wikipedia.org/wiki/AMC_Straight_6_engine#4.0

I saw a post where you recommended that procedure yet 87-88 have like a federal exemption or something found this out after buying vehicle my vehicle was manufactured in 87 sold as 88
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Friday, June 20th, 2008 AT 12:31 PM

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