95TM heads on a 93 block/PCM- need advice

[fireguy12117]

I've posted up a few times about detonation issues that i cannot get figured out. Well, i put a call into the place i got my rebuild from and talked with the service manager who fortunately picked up on the fact that i've done my home work- at least to some extent.

through our conversation it was discovered that i have 95TM heads with my 93 block and engine management. a quick read on the tech pages and a search in here reveals plenty about the fact that this combo WILL cause detonation at lower elevations. Michigan surely fits this.

Can i get this combination to work?

As in, can i get a hold of PCM for a 95 or so ranger and swap that into my 93 to get the fuel management to match with the heads?

What sensors may have changed that i would have to deal with; for example when did sequential fire get introduced that requires a cam synchro? i dont have that, so, what are my limitations in trying approach this problem from swapping PCM's?

my only other option i see is getting them to come up with 90TM heads and a new gasket kit, and getting to work swapping heads. if there is an opportunity to make something happen with engine management via computer swaps, id like to try that route.

 

[AllanD]

A later PCM would be an EEC5 PCM, not EEC4

And it still wouldn't correct the issue, because along with the
smaller combustion chambers of the 95-up heads the 95-up
blocks got a larger dish in the piston to compensate.

There is an "octane adjust" shorting bar in the wiring harness,
looks like a spout connector, but a spout disables the computer's
ability to adjust timing while an octane adjust shorting bar being
removed introduces a fixed ammount of spark advance reduction.

Failing that you can either run premium gas or move to Cheyenne,
Denver, Flagstaff or Albuquerue.

If I ever move out to where my brother and his family lives
in Wyoming I'd build an engine exactly like the untentional
one you have before I left.

An engine like that really is the cat's ass at altitude.

AD

 

[fireguy12117]

yeah well not so much cats ass in flat ass Michigan

i tried the octane adjust jumper and it didn't do much for me, it still detonated on the freeway.

spout connector i haven't messed with since that jumper more or less emulates a failure in the ignition controls and like you said, puts the timing at 10degrees flat.

and you answered perfectly. i thought that idea was too good to actually work- i knew there had to be something preventing such a simple swap from making this head/block combo work.

it more or less looks like i am down to having that shop find me some 90-93TM's...

well, i think ill try a tank of premium since i have now seemingly gotten the root cause for my detonation. i am still going to double check the O2 sensors for operation- just in case. i thought MAKG said there was a possibility for a failure on those not detected by the PCM.

 

[AllanD]

Hey, if anyone starts selling Bio-butanol/gasoline mixes you are ready to rock.

OR if you want to convert it to propane....

Other than that I'd go to your engine builder and complain.
that engine was simply built "wrong".

Not to far in the distant past I sold a guy a set of the early heads
(known good) for him to put on a late block...

That engine wasn't going to be used in the US.
He was taking it to central america to replace a 2.8
and didn't think much of the local fuel...


AD

 

[fireguy12117]

how funny, i seem to be at a somewhat interesting cross road. i really thought i might have had a chance to pull something off as soon as you clarified the point about the pistons being matched to the older block. even with a programmer, i don't think there is enough of a benefit to waiting for new fuels, or paying for a programmer just to keep a certain set of heads.

I am going to call them today and have them work something out.

i'm just friggin glad i got to what seems like the bottom of this crap. i don't know how many times i have read the detonation posts and posted my own threads on this damned topic, how many times I've read diagrams, troubleshooting guides, and just stood there staring at the engine wondering what i missed...good lesson learned, but i don't know that i would have known to look for that 1.5 years ago when i picked up the motor.

maybe i go to the junk yard and get that lower intake off of that 95 sploder i'll be ripping this truck apart again soon

 

[Edgefevah]

what would be the result of having 93TM heads on a 95TM block? i just took my heads off to change gaskets and found out that my block has the deeper dish piston.

 

[Edgefevah]

Well I have bought a set of heads for my truck from gerry over on Rangerpowersports and still waiting for them to come in the mail but they are 98TM heads that are P&P and have dual springs, stainless valves and are as sexy as can be!!!!! Will be getting a 422 CAM and new pushrods, should make for some awaking POWER!!!!!