constant miss and other issues

[jsawyer1181]

Ok, here's the deal. I just bought a 94 explorer and did the plugs and wires. I thought it would have taken care of the misfire but it didn't. The truck has just over 160k. Here's what I noticed, it has what almost sounds like a manifold leak if some sort that ticks in rhythm with the misfire. I also have gas smell near the back drivers side of the engine. Now my question is could this be a bad intake seal? Fuel injector? Or coilpack? The plugs looked old but not black or anything. Also on the waived emissions report it had high hc levels at idle but fine at cruise speed? Sounds like it only runs on 5 cylinders at idle. Also looked like they tried yo change only one plug wire to fix the issue but didn't.

Any ideas?
I don't wanna take everything apart for nothing.
Thanks
Jeremy

 

[johnnytulips]

rich at idle could be the fuel pressure regulator leaking into to intake throught the vacuum line. that could cause a random misfire at idle even a no start cause it can flood it. is it the same cylinder missing at idle? if so check the kv to that plug or check if the plug is wet or white. if all ok then check compression in comparison to a known good cyl. there notorious for cracked heads with high mileage. already replaced mine found a crack between the valves. good luck.

 

[jsawyer1181]

It sounds like it's the same cylinder that misses every single time. The plugs are new but the old ones had like a bit of ash on them. Idk if the heads cracked IR not cuz there's no oil mixed or overheating. Runs fine once u get above sat 2100 rpms. But u can definitely hear a tick that sounds like if u have a leak around a spark plug when it's running only not as bad. Could a fuel injector do this? What about the fuel smell?

Thanks.

 

[johnnytulips]

since its the same cylinder. you pull the wire to that cyl n check the kv. good kv will jump at least a 1/4inch gap and have a nice blue color, bad kv is orange. if thats good. then spray carb cleaner or 2+2 on the area of the intake seal of that cyl. if it improves or boggs out then theres a leak. still npf then to check the injector you do a relative resistance check or check the pulse to it with a noid light and check the flow of the inj ground it out and watch the fuel pressure drop. you can listen to the inj click with a long screw driver directly on the injector the rail will makes clicks from the other injectors. also check compression or even a runnig compression test.

 

[johnnytulips]

the fuel smell and tick noise could be a small crack or leak in you exhaust header.

 

[jsawyer1181]

Ok I had a chance to take a closer look. Here is what I found. Cylinder 6 isn't firing AT ALL. Coilpack sparks no problem. Sounds like I have a exhaust leak coming out of cylinder 6 on the exhaust manifold so its not a gas leak like I thought. Its getting fuel as I pulled the plug and it was black/dark brown. So I guess I need to know what I am looking at here. Are we talking bad valves, cracked head on cylinder 6, blown headgasket (doesn't overheat or mix fluids) or? I'm at a loss. Attempted a compression test but didn't get a reading on that cylinder and wasn't sure if it was a defective tester or whatnot. Would hate to send it to the wrecker when the engine is what seems to be the only major issue with this truck. If it was the block would I have like blue or white smoke coming out of the exhaust? It doesn't smoke.

Thanks.

 

[johnnytulips]

try a cylinder leak down test. theres a tool made just for it. or just put air in the cylinder a put the cylinder to tdc on the compression stroke and listen for air coming from the radiator cap, oil fill cap, throttle body, dipstick tube, or exhaust.let me know what happens from that.

 

[jsawyer1181]

From what I have been able to tell (from various tests and the obvious) it has a burnt valve on cylinder 6. It has a exhaust leak at the manifold where it mates up to the head and I believe that is what caused the valve to burn. So what I am going to do is have the engine replaced. Might be easier then replacing the heads. I just assume start with a newer engine with less miles. So that's where I'm at. Either that or sell the thing. Thanks for your help.

 

[Currency]

My ex is still stock with 205k miles and climbing. Engine and trans are fine. Perhaps save your old engine and try a complete rebuild later down the road?

 

[rhauf]

replacing a used engine with a small problem (brunt valve) with another used engine in hopes that the slightly newer engine is.... newer, seems a bit of a crap shoot to me.

did you do a compression test? what were the results? have you done any vacuum testing? a vacuum gauge on manifold vacuum may help indicate if you really have a burnt valve or not (google engine tuning with vacuum gauge)

160 isn't bad..

speaking of pulling out an engine with problems to replace it with a slightly newer engine... i recently attempted just that. pulled out my knocking engine and dropped in another. turned out the one i put in had cracked heads.

 

[jsawyer1181]

The compression on all but cylinder 6 were around the 140 range I think. Cylinder 6 had absolutely nothing. I could just put new heads on it but that's more then I care to spend on it at the moment. I know I'm taking a risk putting a used engine in but the way I see it is if it runs for a few years then I got my money back.

 

[BIGTREAD]

...I'll get my money back...were my exact words. The only advice I didnt' get and wish I had was....only rr with same eng, same year, same vehicle. Way too many incompatibilty problems down the road. I'm in the middle of good 98 into a 2000 thats been baffling mechanics since the Spring. So far I've gotten two stumbling months out of my swap.

 

[rhauf]

The compression on all but cylinder 6 were around the 140 range I think. Cylinder 6 had absolutely nothing. I could just put new heads on it but that's more then I care to spend on it at the moment. I know I'm taking a risk putting a used engine in but the way I see it is if it runs for a few years then I got my money back.

i'd be inclined to just pull the head and have the valves in cylinder 6 redone. i'd expect that to cost less than a new (used) engine and it's the devil known so to speak.

 

[johnnytulips]

if you have zero on one cylinder. most likely a cracked valve spring or rocker came off seen it before mostly on GMs.do a vacuum test,if the gauge bouces at least five in hg pull the valve cover and check could be a quick fix. best test to do is a cylinder leak down test.