I swapped my auto trans out for a manual on my stock '88 CRX DX a while ago and have been fighting idle problems ever since. I haven't had much time to work on the car and solve the problem, but on a hunch I decided to double check my ECU to confirm that I have the right one.

I have a 37820-PM5-A080. I can't find any info or chart showing what this is out of though... Is there a list or does somebody know the donor car (I bought it off craigslist as a tested manual trans DPFI ecu...)?

I DID find an ebay listing a 37820-PM5-A060 as a stock 88-91 CRX DX Manual trans ecu.... Is there a substantial difference between the A060 and A080? Maybe one is designed for different sensors and that's throwing things off enough to affect my idle?

Any input would be appreciated. Now that it's warming back up I'm ready to start driving the car on a regular basis again....

 

Nobody knows?

 

http://www.hondata.com/techecuid.html

 

Maybe when u changed the trans u broke a vacuum hose. I would check the vacuum lines or adjust the idle screw

 

Checked Vacuum lines already. Not only none broke, but they are all nice and pliable. I've adjusted the idle screw down a bit, but that's def not the problem. The base idle is right around 750, but something is keeping the idle up, especially when the weather is cold.

 

That helps... Thanks. At least I know the PM5-A080 is a manual trans CRX ecu... Of course I still don't know if there are any differences between the revisions that might be affecting things.

It's a start though. thanks again.

 

Could it be an MPFI ecu and not a DPFI ecu? I don't know if MPFI was OBD0 or if a dpfi car would even start with an MPFI ecu, but since the '88-91 CRX's came with both systems depending on model, I guess it's a possibility I should at least check out....

 

PM5 is for the DPFI
PM6 is for MPFI
PM8 is for the HF MPFI

 

Thank you for that. One more possibility eliminated.

I've been out of town (again!) all week, and will be leaving again tomorrow night. Maybe if I'm lucky I'll get a few hours to spend actually working on the car next week. Until then, it's just "mental diagnosis" and looking for things to check.

 

sooo thought I had the problem solved, but alas! No luck....

This morning I tested the temp sensors, they're both good. When I checked the TPS on an oscilliscope though, it was pretty wacked out near idle. After finding out that nobody in town stocks TPS sensors for this car (???), I tracked down a good used one, tested it to confirm it works, and installed/calibrated it with high hopes that it would solve the problem.... NOPE! No change at all. The idle is still high and erratic.

I think I'm back to either a bad ecu, or a wiring problem (remember, I did an auto to manual swap and ecu swap)...

Can anybody post links or pinout diagrams for an automatic 88 crx dx and a manual 88/89 CRX dx manual? I have looked and haven't been able to find anything that differentiates between the two.... The only differences I know about are the backup light and neutral lockout, and that's all I changed when I did the swap......

 

timing perhaps?have you cleaned out the IACV(Idle air control valve)or any of the hoses leading from the intake manifold,i had a d15b2 that had **** clogged up in there.Took most of it apart cleaned it all up Ran better and idled smoother;just some food for thought.Matt

 

Cleaned it out right after the problem started (the first time I drove it after I did the swap), and then again today. I also bench tested it this morning and it appears to be working as designed. From removing and replacing it, I know the lines aren't clogged since I'm getting clean, warm coolant flowing out of the lines.

Timing hasn't been touched since I bought the car. I left the dizzy in place when I did the swap.

Also, I don't know if it was the warm weather, or something else, but this afternoon it started surging between 1000-1500 rpm constantly (in a traffic jam of course!). That's a new symptom, but it's the first time I've driven it in 70+ degree weather as well.

 

Crap...

The ecu has been eliminated (tried swapping it)
O2 sensor eliminated,
ICV eliminated,
temp sensors eliminated,
bubble in the cooling system eliminated,
Wiring mistake eliminated (I think!)
throttle linkage eliminated,

I'm at a loss here. Does ANYBODY know what might be causing a high/surging idle?

FWIW, I've found out that it appears to get worse at higher temps or lower altitudes.... Traveling to Phoenix, the high idle was up to about 2600-2800 rpm, and blipping the throttle would drop it but cause it to surge between 1000-1500 rpm. Home in Flagstaff, after a few restarts, the problem returned to the old symptoms... high idle around 1400-1800 and blipping would drop it to about 750 with usually no surging....

HELP!!!

 

Hi there, I am new to this Honda tech and if i can help then great. I have 91 accord and had a similar problem as where the idling surges. After changing almost everything on the intake, (fitv,iac,etc) I still had a problem.

Determined to fine the problem I took my throttle body off and checked the adjustment for the choke valve. I found that the choke in closed position(not pressing the gas pedal) position, was actually open a little. so i took the tiny adjuster screw off. now the choke was in closed position. I put the screw back in until it touch the choke plate and put it up like half a turn. You know what it worked. My engine runs great and no more idiling problems. Now i know these adjustments are usually not touched from the factory setting but you never know. Take a look.

Had this problem on my two 91 accords.

 

Not sure what the choke valve is or wether there is one on my car.
... Is your car dpfi or mpfi?

 

No explanation about the choke valve?

As an update, I've tried re-adjusting the base idle and that didn't improve things. I'm running out of troubleshooting ideas fast.

One item I've yet to address. The temp sensors both were in range, but when I disconnect the air temp sensor, it makes hardly a difference in the idle. Can somebody else with a DPFI car maybe pull the plug on their air temp sensor and see if it changes the way the car idles?