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rough idle at stop light and stutter under acceleration


pbtexan
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Hi Team !

 

History:  89 Reatta   18,300 miles, owned two years (bought at 11,600 mi)       

At 17K miles, developed a stuttering problem in light throttle pressure "mid-acceleration" (40-60 mph).   

Based on generous input from this group, I Replaced Plugs ( they were originals best I could tell), Wires, Coil Pack and ICM (magnavox) about 500-1000 miles ago. 

Ran smooth for several hundred miles - made a road trip from FTWorth to OKC for installation of new radio and speakers and no problems. 

Did not drive for 2-3 months, but was on trickle charger and would start it every 2-3 weeks and idle up to operating temp of 175, then shut off.

 

New issue:  Starts fine, runs well until first Stop light or two.  Sitting at idle, starts running rough.  Has not actually died, but runs rough.  Pull away from stop light and smooths out.   Then will occasionally stutter at light acceleration, then smooth out and run fine.

 

In reading similar problems and responses I'm seeing:   

1) ICM and or coil pack is "still" bad, even though relatively new Magnavox,  Solution:  hunt down and purchase Delco unit.... 

                  ??can I use a Delco Coil pak w a Magnavox ICM?? OR are the coil pack/ICMs a matching unit?

 

2) Fuel issue?;  fuel filter or fuel pump? 

                Not sure if this is it, seems to run strong with no "loss of power" under normal conditions.  It's actually fast and nimble compared to everything else in the driveway !!

 

3) I've seen Daves89  notes on "30 yr old electrical issues"    regarding preemptive replacement of  "MAF Sensor, Ignition Module/Coil Pack, Oxygen Sensor, Crank Sensor".                   Should I skip Coil pack/ICM and go to MAF, and crank sensor?   

                 FYI, I do not have electrical testing skills/equipment, and I'm not sure if I could replace a crank sensor, but I do have a decent mechanic available !  😉

 

Thanks for the guidance ! 

 

I'm thinking of parting with this beautiful low mileage specimen and moving to a convertible, but I want it to be "strong condition" when I post it !

 

Paul

 

Edited by pbtexan
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Correction, the Coil pack was a AC Delco D552   ACDELCO D552 {12353801} (Standard Replacement) GM Original Equipment MAGNAVOX, W/SHIELD but it is the one piece unit not the three piece.

 

The ICM was ACDELCO D1922A {24503623} (Standard Replacement) GM Original Equipment          USED WITH GASKET KIT 25526450.; MAGNAVOX

 

So even though these are Delco, they are Not "Delco 3 piece" coils?  

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11 minutes ago, pbtexan said:

New issue:  Starts fine, runs well until first Stop light or two.  Sitting at idle, starts running rough.  Has not actually died, but runs rough.  Pull away from stop light and smooths out. 

I had a similar problem and it was caused by the MAF sensor. However, since MAF sensors are expensive if I were you I would start by doing ALL the fuel pressure tests in the How-to guides here on ROJ to rule that out. Easy to do if you have a fuel pressure gauge, and it doesn't cost anything. If you don't have a gauge you can get a loaner for your local auto parts store.

 

Since you have replaced the ICM and coil pack I'm doubting that is the problem, but it could be. Have you replaced the spark plug wires?

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"runs well until first Stop light or two.  Sitting at idle, starts running rough. " sounds like about when it goes into closed loop. (left middle indicator on ECM status scream).

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I'd start with the simple things;

1] Check and clean battery connections

2] Check and clean all ground connections starting with what's behind the battery

3] Check and clean the idle control sensor and housing located under the air intake

4] Check and clean the butterfly on the air intake

These are all easy to do items [see the "How to" on the top of the page] that should be checked before throwing parts at it. Your issue doesn't throw a code that we can tell exactly what you are dealing with, but is a good first step before you do more part replacement. 

It looks like a great car, one that I would be reluctant to part with. My Red has over 300,000 miles on it [the vert 130,000 and the Black about 240,000 the last two still on original engine/transmission] so believe me you will get by it. 

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Ronnie  

Yes, spark plug wires were replaced with the plugs and Coil pack.   ICM was replaced a few weeks later when the first three (plugs, wires, coilpak) did not seem to resolve the issue !!

I'll check the how to section an borrow a fuel pressure gauge from autozone !   

 

BTW, can using a new coilpak with an old ICM cause the new coilpak to fail?    Just wondering.

 

Padgett   

I'll check the ECM status screen today !

 

Daves89   

Is there a preferred spray cleaner for these cleaning jobs?   "carb cleaner" or something similar?   I don't want to be the gufus who sprays "brake cleaner" on all the electrics and fries them !  LOL

 

I am reluctant to part with it.... now that I'm retired I am looking forward to some more Short (less than 500 miles here in Texas) road trips and this is such a nice cruiser !  

 

But I am caught in the issue of "reliability anxiety" regarding these electrical gremlins....  I have a modest tolerance for most issues, but when my wife is traveling with me, she has bad reactions (stress stomach) to breakdowns.  

 

I actually got rid of a very nice 89 Mercedes 300 CE because the electrical gremlins led to 3 or 4 tow jobs and when finally resolved, I had already lost faith in its ability to be reliable !

Edited by pbtexan
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31 minutes ago, pbtexan said:

 

 

BTW, can using a new coilpak with an old ICM cause the new coilpak to fail?    Just wondering.

 

 

That is a subject that has much mixed messaging. I suspect many of us, myself included, have mixed new and used parts with some success. There are youTube videos diagnosing and repairing ignition systems like ours on the internet, and the general consensus is they should be replaced as a set. The Delco triple coil is seemingly designed to allow replacing single components?? The jist of the story seems to be that a failing coil or coils, puts more strain on the ICM which may then fail prematurely after the coil is replaced. Clear as mud, huh?

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43 minutes ago, pbtexan said:

Ronnie  

Yes, spark plug wires were replaced with the plugs and Coil pack.   ICM was replaced a few weeks later when the first three (plugs, wires, coilpak) did not seem to resolve the issue !!

I'll check the how to section an borrow a fuel pressure gauge from autozone !   

 

BTW, can using a new coilpak with an old ICM cause the new coilpak to fail?    Just wondering.

 

Padgett   

I'll check the ECM status screen today !

 

Daves89   

Is there a preferred spray cleaner for these cleaning jobs?   "carb cleaner" or something similar?   I don't want to be the gufus who sprays "brake cleaner" on all the electrics and fries them !  LOL

 

I am reluctant to part with it.... now that I'm retired I am looking forward to some more Short (less than 500 miles here in Texas) road trips and this is such a nice cruiser !  

 

But I am caught in the issue of "reliability anxiety" regarding these electrical gremlins....  I have a modest tolerance for most issues, but when my wife is traveling with me, she has bad reactions (stress stomach) to breakdowns.  

 

I actually got rid of a very nice 89 Mercedes 300 CE because the electrical gremlins led to 3 or 4 tow jobs and when finally resolved, I had already lost faith in its ability to be reliable !

Carb cleaner, but be careful as the screws are stainless steel so a magnetized screwdriver won't work to your advantage. Put a towel or old shirt underneath the housing to catch the screw if it slips from your fingers. If you should lose one the screws that hold down the MAF sensor are the same.

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59 minutes ago, pbtexan said:

Is there a preferred spray cleaner for these cleaning jobs?   "carb cleaner" or something similar? 

Carb leaner is good but the old style carb cleaner could damage your O2 sensor if you don't get all the cleaner out before running the engine. Check the can to see if it is safe for O2 sensors.

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1 hour ago, pbtexan said:

But I am caught in the issue of "reliability anxiety" regarding these electrical gremlins....  I have a modest tolerance for most issues, but when my wife is traveling with me, she has bad reactions (stress stomach) to breakdowns.  

Don't give up on it. It's going to be OK. Just make sure you have a cellphone and some necessities with you. AAA is a good thing to have as well. I carry a lot of stuff just in case of a breakdown. Probably too much because my trunk is always full. Lots of tools and FSM for diagnosing problems, jumper cables, lawn chairs, WATER, a few spare parts, and a change of clothes. It's better to have it and not need it, than need it and not have it.

 

trunk contents.jpg

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Thanks for the tips on the carb cleaner, will check the fine print !

 

Re AAA,  I have the car now insured with Hagerty's,  I'll check but I think the policy includes roadside assistance !  That WILL be more peace of mind.

 

Padgett,  nice tool kit !!   IS it craftsman, kobolt, harbor freight, northern tool or ?  that sells the complete kit.  I have most of the parts in my garage, but not in a nice kit form !

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1 hour ago, pbtexan said:

Re AAA,  I have the car now insured with Hagerty's,  I'll check but I think the policy includes roadside assistance ! 

I have Hagerty to. If you are a member of their drivers club you get 25 miles of free towing. I dropped the drivers club and went with AAA to get 100 miles of free towing. I do miss the Hagerty magazine that came with the drivers club.

 

 

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I have AAA premier. 200 miles towing (once per year, 100 miles after) on any car I own (or am in).

ps as link says, is from Harbor Fright. Look for 20% off coupon. It fits under the trunk rear shelf.

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6 hours ago, Padgett said:

This fits nicely in he trunk. I have several. Is often on sale.

hftools.jpg.fac5df16968c034a30f938b73941e3ec.jpg

I have a junking bag in my car. As a parts puller from junk yards I have built up a collection of tools needed.

 Regarding parts I carry, they are: alternator, correct length serpentine belt and A/C bypass serpentine belt, MAF sensor, Delco coil and ignition module.

 

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It is hard to predict what parts you will need when you are broke down on the road. I have a MAF sensor, an alternator belt, a relay that fits the brake pump, fuel pump and other stuff, a new spark plug and wire, assortment of fuses, wire splices, heat shrink tubing and black tape. And thanks to Dave I have a complete Delco ignition, ICM with coils mounted on it. I saved room for it in the bottom of the box. Dave's got me beat carrying an alternator.

 

Here is what is inside my toolboxes. I doubt many people carry a fuel pressure tester and a hose to add a can of Freon. 🙂 

 

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SAM_3870.thumb.JPG.3b7c9a9f2715d9025e08959dced3622a.JPG

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I travel a lot in the course of sales calls [sometimes 200 miles or more round trip] and twice in my 50 year sales career been left stranded with a alternator gone bad [once with the Reatta and once with a Roadmaster]. Alternators are not stocked in parts houses anymore and are easy to carry and quick and easy to replace. I have a plastic milk crate I carry in my trunk with extra parts and a tool bag with tools needed. I've been junking for 15 years now and have pretty much all the tools needed to strip a Reatta so I feel comfortable that I have what I need for most repairs. 

 What I should add is a crank sensor and spark tester. That way if I do break down I would have that part as well.

 Something to think about...

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Thanks !  Did not catch the link previously !  I'll drop by and get one !

 

May need to add the triple A coverage !   I'll keep that in mind !   I'll add the Alternator to the carry list. !

 

thanks for the help as always !  I"ll touch back in a couple of week when I've had time to try some of these fixes !

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I carry an alternator rebuild kit. Have been through many. CTS uses a wierd (PWM controlled)  Denso. GM sold off Delco & acre has been razed.

Don't know how many of those DVMs I have, used to be freebies.

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