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No acceleration and low power 2.5L by RCW
Started on: 05-05-2008 05:47 PM
Replies: 11
Last post by: RCW on 05-07-2008 10:53 PM
RCW
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Report this Post05-05-2008 05:47 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
O.K. I am crying UNCLE!.

I thought I was a smart cookie and could figure this out myself. I am what I would consider a pretty good mechanic but this one has got me stumped.

Here is the story.

Purchased an 87 notchie with a 2.5L and a 5 speed about a month ago. P.O. said it was low compression on #1 cylinder. He had replaced the engine a few years ago for the same thing. He was driving around with the new engine installed and heard a pop and low and behold no power. The “new” engine is a used engine form do not know where. It is a DIS engine and appears to be correct for this application. I even got the old engine in the deal. Looks like he swapped them out completely. The manifolds, sensors and ignition system are still on the old engine.

Here is the problem. It starts and idles very smooth when cold and starts to idle rougher as it warms up. Not bad but does rock around a bit. When you try to drive it there is no get up and go. It is very sluggish. The car will go 70 MPH plus but you won’t be getting there very fast.

Here is what I have done. Changed out plugs and wires. P.O. had some kind of wiz bang super duper wires and those 4 electrode plugs. I installed regular plugs and stock replacement wires. The old plugs looked pretty good though. The end plugs #1 and #4 looked very good I would say almost on the lean side. The two center plugs #2 and #3 looked a little less than stellar but acceptable maybe a little rich.

Checked fuel pressure and it looks good 10 PSI. Even changed the filter.
Compression is between 160 and 170 on all cylinders.
Good steady vacuum at idle and at 2000 RPM with no drop from idle.
Went to exhaust shop and they were certain a plugged CAT was the problem. Had it replaced and then they decided I may have another problem. Yeah, the new CAT didn’t fix the problem.

No codes in the computer.
Throttle opens all the way with the gas peddle.
Swapped out the MAP sensor with another one I had. Don’t know if it is good or bad but made no difference.
Brakes are not dragging.

When it idles the exhaust smells rich.

I plug in my scan tool and can see the O2 sensor switching between lean and rich with engine running at 2000 RPM.

The Injector does not seem to be leaking.


Alright folks, I need help.

Ed

[This message has been edited by RCW (edited 05-05-2008).]

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2farnorth
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Report this Post05-05-2008 08:06 PM Click Here to See the Profile for 2farnorthSend a Private Message to 2farnorthDirect Link to This Post
Have both of your coil packs and the module tested. Sounds like one of the coil packs is breaking down as it gets warm. By the way if the 4 prong plugs that you took out were bosch platnums sell them to someone that can use them. DIS Dukes hate those plugs. I really think they are a waste of money in most applications. Your standard AC's are as good as it gets for that engine.
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spark1
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Report this Post05-05-2008 08:32 PM Click Here to See the Profile for spark1Send a Private Message to spark1Direct Link to This Post
Coil pack is a good place to start since 1 & 4 are in one and 2 & 3 in the other.
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RCW
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Report this Post05-05-2008 10:29 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
VIOLA!

I went out and did some more testing. You know if you follow the trouble charts in the factory manual they will take you to the problem. A friend of mine that owns his own marine and machine business once told me that when you are trouble shooting you need to forget about the "wouldn't be, shouldn't be and can't be".

Engine at operating temperature. Unplug IAC, pull plug wires one by one and watch for RPM drop. Well, #2 and #3 made no difference. I have some extra coils so swapped one out. Still no difference. Pulled the DIS and took to Auto Zone and had it and the spare one I have tested. Both are no good. Had a new one out of the box tested before I bough it and it passed. Took it home, installed it after I double checked the coil resistance and put a fairly close matched set on. Car runs like a champ!
So, $450 for the car, $189 for a new CAT, about $50 for plugs and wires and $99 for the DIS module and I have a nice running Fiero






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Fierobsessed
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Report this Post05-06-2008 12:33 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedDirect Link to This Post
Excellent!

Arent you glad that the Fiero is not a 2 cylender like yours was?
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RCW
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Report this Post05-06-2008 03:56 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
Fierobsessed,

Man, what a gutless wonder that was. It is really amazing what a difference two cylinders can make.

Was wondering though, what caused the DIS failure. I noticed that the heat sheild is missing that goes between the trunk and engine above the muffler. Could the heat from the muffler caused the DIS and or coils to fail?

I never had the heat shields out of any of my other cars. Is there just the one or is there two of them that go between the trunk and engine compartment? I see a couple of them for sale on EBay and not sure if I need one or two.

Can anyone shed some light on the heat sheild issue? Any pictures would be great too.
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Fierobsessed
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Report this Post05-07-2008 03:12 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedDirect Link to This Post
That heat shield does not help or hurt the ign coil, there is enough distance between the coils and the muffler to sit comfortably. Most FWD cars actually have the coils and ignition module stuffed under the exhaust manifold behind the radiator. Could they pick a worse spot?

In your case, if the module and the coil both failed together, I think that somehow water got into the coil, causing it to short out, and that will inevidably burn up the transistors inside the ignition module. Perhaps something else shorted out on the coil? Best bet, do a resistance test on the coil. if it is shorted, maybe cut the coil up to find the root cause of the failure I mean, If you feel like it.
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RCW
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Report this Post05-07-2008 10:28 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
Hmmmm.

Not to be argumentative but, why did Pontiac put the heat shield in there? I know that heat seems to take out the modules on the V6 cars. But on the other hand I have heard of cars with the original module and still running fine. No rhyme or reason to it I guess.

I was just considering that the previous owner had replaced and engine for what he said was the same problem. The module off the old engine was bad as was the module on the engine in the car now. He said it was running fine for awhile. I don't remember what he told me as to how long it ran before it had a problem. Course he thought the engine was low on compression and had been trying to get it running for several years and gave up. It had not been licensed since 2004.

So, do we think that maybe something else is taking out DIS modules besided heat?

The coil was not bad but just a little out of range on the resistance test. I think the spec that came with the new module wanted between 6.0K and 11.0K ohms between the output towers on the secondary side and it had 5.8K. the ones I matched up were at 6.3K and 7.1K.
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Report this Post05-07-2008 10:37 PM Click Here to See the Profile for 86fierofunSend a Private Message to 86fierofunDirect Link to This Post
Something else is probably blowing the coils.

I just wanted to say that I love the paint color! And the rims!! Awesome car!
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RCW
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Report this Post05-07-2008 10:44 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
86fierofun,

Thanks, I liked the color the first time I saw it on Craigslist for sale. Guess I talked myself into it before I went to look at it in person.
Not even sure what brand the wheels are the center caps say "EAGLE" on them.

I thought the deal on the car was pretty good at $450 and I drove it home. Sweeeeet!

[This message has been edited by RCW (edited 05-07-2008).]

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RCW
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Report this Post05-07-2008 10:51 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post
Here are the wheels I put on the 86 GT you see in the backgound.


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Report this Post05-07-2008 10:53 PM Click Here to See the Profile for RCWClick Here to Email RCWSend a Private Message to RCWDirect Link to This Post

RCW

190 posts
Member since Apr 2008
I wonder if those Bosch Platinum plugs with the four electrodes could have overtaxed the igintion coils and the DIS module?
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