High idle and emissions on 2.8V6 (Page 1/2)
br1anstorm APR 18, 06:32 AM
Not for the first time, I'm trying to diagnose a high idle problem. But I'm not an expert engineer, so I'd welcome some step-by-step advice.

I have a 1988 Fiero Formula (2.8V6). The catalyst was removed some ten years ago, and replaced by a standard muffler pipe.

A couple of years ago, the engine used to idle when cold at between 1500 and 1800 rpm (sometimes higher). I discovered that the EGR tube was leaky/corroded. I replaced it with one from Rodney Dickman, and that seemed to improve matters slightly.

I haven't used the car over the winter, but it now seems to be suffering from 'high idle' again. The other possible clue is that the engine has always run very cool (at least according to the temp gauge, where it barely reaches the second marker-line on the dial). When stuck in traffic or idling in Park for a long period, it does warm up closer to the midway point on the gauge, and when it is that hot, the idle speed drops to around 850-900 rpm.

The latest annual roadworthiness check indicates that the emissions are close to, if not over, the limit, so something needs to be done!

To my simple mind, the evidence suggests that the engine is running "rich" - as if there was too much choke (except that there is no manual choke). I don't have the expertise to run a WinALDL scan. What other checks can I do, and in what order, to try and identify the cause of the high idle/running rich/high emissions problem?

[This message has been edited by br1anstorm (edited 04-18-2018).]

Crasian APR 18, 10:57 AM
Probably vacuum leaks. At my repair shop we use a “smoke” machine and that allows us to find all sorts of broken lines, torn gaskets, etc. We even use It to find exhaust leaks in a similar fashion. My ‘88 had all kinds of air leaks in the intake and exhaust system, it would fail the emissions like crazy. Fixing all the leaks cured nearly all of my issues...

[This message has been edited by Crasian (edited 04-18-2018).]

olejoedad APR 18, 11:02 AM
If you have access to an OBD1 scan tool that reads sensor values, check the inlet air temperature readings.
Patrick APR 18, 01:18 PM

quote
Originally posted by br1anstorm:

Not for the first time, I'm trying to diagnose a high idle problem.



Yes, it seems we've been down this road before. High idle on my 1988 V6 2.8


quote
Originally posted by br1anstorm:

I don't have the expertise to run a WinALDL scan.



It doesn't take much "expertise" to read the values for things such as Manifold Air Temp, Coolant Temp, etc. Just using the most basic aspects of WinALDL can be most helpful when troubleshooting.

[This message has been edited by Patrick (edited 05-03-2018).]

br1anstorm APR 18, 05:58 PM

quote
Originally posted by Patrick:

It doesn't take much "expertise" to read the values for things such as Intake Air Temp, Coolant Temp, etc. Just using the most basic aspects of WinALDL can be most helpful when troubleshooting.




Hmmm, we'll see. I have the necessary cable, and the WinALDL software on an old laptop. But it doesn't exactly look like "Plug 'n' Play" . It's the setting-up that looks like witchcraft to me.
Patrick APR 18, 06:15 PM

quote
Originally posted by br1anstorm:

Hmmm, we'll see. I have the necessary cable, and the WinALDL software on an old laptop. But it doesn't exactly look like "Plug 'n' Play" . It's the setting-up that looks like witchcraft to me.



You've even got the cable! Well damn... it's not that bad!

Is your cable USB or serial? The biggest nuisance (sometimes) is simply configuring the laptop to the correct COM port.
br1anstorm APR 19, 02:13 PM

quote
Originally posted by Patrick:

You've even got the cable! Well damn... it's not that bad!

Is your cable USB or serial? The biggest nuisance (sometimes) is simply configuring the laptop to the correct COM port.




Ah, when it comes to spare parts and bits 'n' pieces (I have other cars besides the Fiero) I collect and hoard anything that might come in useful or might go out of production. You should see the roof-space in my garage.... everything from spare windscreen to headlight motors.

So yes, I got a cable (from Dodgerunner IIRC) a while back, reckoning that sometime I would have to get around to using it. Has a serial connector, which I hope will be OK as I have at least a couple of old laptops (one Win98, one XP) which have the right sockets.

Hence my search for advice... but many forum posts seem to consist of geeky esoteric dialogue between people who already know what WinALDL is and what it does and what the readings mean! I am still at the stage of trying to figure out (a) the physical connections, the ports, and what plugs in where, which seems pretty straightforward (provided I don't have to mess around with extra resistors...); (b) the actual setting up of the WinALDL program, ie what parameters or engine codes have to be set, or is it just a matter of using the default settings? and (c) the big banana: understanding the results, whether a row of numbers or a line on a graph. Until you know what the normal readings should be, you have no chance of spotting any discrepancies or knowing what caused them or how serious they might be.

Maybe this weekend will be my trial run with this unfamiliar technology......
Patrick APR 19, 03:20 PM
As long as your laptop has a serial port, the serial cable you have is actually preferred over the USB version. Seems to be easier to configure the COM port etc.

Have you got ALDLView? If not, click on that link to read about and download it.

[This message has been edited by Patrick (edited 04-19-2018).]

br1anstorm APR 19, 06:24 PM
Thanks Patrick - have just gone to look at ALDLView and have downloaded and installed it. Looks as if it will help to make sense of whatever numbers emerge from the logging.

Steep learning curve this weekend, I suspect!
Patrick APR 19, 06:36 PM

quote
Originally posted by br1anstorm:

Steep learning curve this weekend, I suspect!



I haven't hooked mine up for years. I'll run through the process tomorrow... so maybe if you have any questions I'll know what's going on.