EFI problems. :(

[Grim-Reaper]

I was supose to be going to pick up a 1968 Poncho 400 punched .040 over with a 400 H.O.cam Highrise intake, Demon 750, 6X Heads and headers for my 70 LeMans Sport drop top with the truck this weekend.

88 454 Burb. Doesnt idle up like normal when you try to start. Once it strts it bobbles REAL bad like its firing on 4 cylinders Then it suddenly clears up throws the Check engine light but goes to warm idle speed.


Here is the kicker. Its storing no codes but gives me the code 12 like its supose to.

Testing it running its going closed loop like its supose to.

Anyboy see this before?

Book says the QUAD IC might cause these symptoms and my ECM is not protected so if something shorted out it would FRY the ECM. I have a spare ECM but got to do the diagnostice to make sure I don't smoke it too if thats what has happend.

Anyway any pointers would be much appreciated. I don't have access to WinADSL so I'm doing paper clip diagnostics.

 

[Grim-Reaper]

Man you guys are letting me down. posted this last night and only 28 people looked.

Top

 

[Thunder]

Check/replace your Distributor module before you do anything else.

A CEL and no codes except the usual 12 is usually the dist module.
Could also possibly be the pick up coil.

 

[Grim-Reaper]

Check/replace your Distributor module before you do anything else.

A CEL and no codes except the usual 12 is usually the dist module.
Could also possibly be the pick up coil.

Really? the Manual said No pick up in the disttributor and it should throws crank sensor code.

For no codes like it did last night it says it is most likely the Quad IC control chip that runs the IAC, EGR Solonoide and a couple other things.

Its fixed.

Got to love dumb cheap problems. This is 100% age issue. Thes Sub just rolled 84,500 miles. I put a grand total of 3,000 miles on in in the last 12 months.

What still perplexes me is no codes last night. I checked it 4 times AND I tesed it to make sure it was going closed loop.

I checked it this morning and it had Code 33 in it. MAP sensor.

I get looking and the vacuum hose going to the Map and heat bad baked it into a brick. It cracked and fell off the Throttle body side where you couldn't see it. I missed it the first 4 times I was looking for issues. So 50 cents of 1/4inch Vacuum hose later its fixed.

As bad as this was I think it was sucking air past it for quite a while. Proably throwing off the MAP sensor reading. I had infact questioned the MAP sensor well over a year ago because of a few other off and on issues. I was going oit replace it and the mechanic at the Local dealer talked me out of it. I found a Vacuum leak else where just like he suspected I would so I never really inspected it. Now I am curious to see how it runs and if the echonomy comes up. Its been getting short tripped A LOT the last year and avg 8mpg. Hope that comes up.

So either I'm just a ditz and can't count or it didn't throw that code last night. No code put me into panic mode. If it threw a MAP last night it would not have bothered me in the least. I need to test this other ECM out an make sure its good and keep it handy as a spare. I'm still not coviced I don't have a issue with the ECM.


Wife has driven it much more then I have in the last 6 months. Usualy have the family in it the rare occasion I drive it so I take it easy so as not to upset the wife unit. Its amazing just how quick a 6K sub with 3.73's and 31.5 inch tires can get up to 60mph when the skinny hits the floor. Freaked out a ricer on the test drive. Pulled out just as he passed me going about 45mph next thing he knows I blew past him LOL. Runs scarry good now.

 

[Thunder]

Really? the Manual said No pick up in the disttributor and it should throws crank sensor code.

Might want to check what year manual you have. Either that or it has some bad info in it. 88 TBI has NO crank sensor and Does have a pickup in the dist.

Anyhow. Glad you got it fixed.

 

[eagle mark]

Glad your running! Vacuum leaks are a huge problem with diagnosing efi problems.

Next take a look at the TBI gaskets and tighten or replace. The BB TBI has much less gasket do to the larger bores and are common trouble makers...