FI problems.

[Darrell Tuxwwor]

I am having a few operational problems with my Howell FI system. The system has been on the Scout for about 6 years but has never really run to my satisfaction. It isn't consistant. Any how here a a few questions.

1) Usually at home, 6500ft, cold start it goes up to 11-1200 rpm until it starts to warm up then idles down BUT if I go up 2000ft or more cold start is at about 800 RPM. warm idle is fine Any ideas?

2) What wave signal does the ECM get from the coil? IE square or what and what duty cycle and does it matter?

3) Does the ECM or the program have any sort of a rev limiter? I actually think this problem is related to the MSD but not sure yet.

4) Why might an engine on cold start all of the sudden quite going to cold idle and idle lower than normal hot or cold idle? It is idleing about 5-600 rpm. Also when it starts cold or warm it catches but idles up slowely. It acts just as if you would just bump the starter on a carbed engine and the engine was turning so slow there wasn't much air speed throught the ventiries but there was enough fuell,, air and spark for the engine to just start to turn over on it's own but it takes a second for the engine to get up to speed.

5) A couple of times after the engine has been running for hours it will all of the sudden jump up to a high idle of about 1600 RPM or so and I can't get it to come down by restart or slamming the throttle, like you would on a carb to free a stuck throttle.
Well thanks for reading this far. I think this should be enough questions for now...
Any ideas are greately appreciated.
Once I get the remodlator and all the related stuff to burn my own chips I should be well on my way to getting this thing running superbly.
Darrell

[Bill usn-1]

You may need to start by getting the winaldl program and building the cable.
You will need to log the data from the computer so we can see what it is doing.
A couple things to keep in mind is how does howell set up the computer and harness for the vehicle spd sensor(VSS) and the park/neutral wire.
check out pin A10 and B10
[IMG]ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/747ecm1.jpg[/IMG]
pin out diagrams.
You will need to get familiar with what information the computer will give you, then decide what you want to change.

ftp://ftp.diy-efi.org/pub/gmecm/manu...47/747ecm1.jpg

[Eagle-Mark]

A laptop computer with WinALDL would give you lots of information including data for burning new chips but there are other simple (cheap) ways to look for problems as well.

Some of the things you are saying seem familiar with some problems I had when first start up which all revolved around vacuum leaks. Check out the troubleshooting section from AFI.
http://www.affordable-fuel-injection...-injection.htm

Also the high idle that you must slam the throttle? Wonder if the throttle plate shaft is worn, just like a carburetor.

One more thing. Does the Howell system have a check engine light? Something everyone needs to learn how to do when they become fuel injected is how to check for codes. You don't need a laptop or expensive equipment for this, just a paperclip. Read the "How To" including the codes at:
http://www.affordable-fuel-injection...jection.htm#14

[TwoFast4Lv]

Well if Howell programed it last I would definately start with a known good program.

Then I would follow the above advise.

We have not had the best luck with howell

[Bill usn-1]

I burned his last chip for him in Co while we were at the RMIHR.
He still has the stock Howell chip to try.
Just talked to him and he is concerned the ECM may have gotten damaged from an overvoltage from the MSD.
Even with his foot to the floor the computer is constantly firing the injectors.
He just installed a tach adapter to make the MSD signal more compatible with the TBI.
I suggested he pull the chip and see if the motor runs any different. This would help determine if he was in limp home mode.