When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
my 92 had the same issues a couple months back. It would start and idle fine but if you stepped on the gas it sputtered big time, until it got to 120 or 130 degrees, then it was fine. mine didnt have any codes either. I changed out the coolant temp sensor and the throttle position sensor and that fixed it. inexpensive parts and easy fix.
Its on the head, mine is on the passenger side, rear part of the head, between the the number 6 and 8 cylinders. Service manual says its on the drivers side between numbers 1 and 3. I wondered if my heads got switched. Its a gold colored plug that sticks out of the head.
If its running awful cold, its an open loop issue. CTS in the intake manifold, TPS/IAC, and perhaps a stuck open Cold-start injector which would be odd that its only that one. Everything the computer does is based basically off the CTS and TPS values it reads, and preprogrammed tables in memory.
TPS should be 0.54V at idle, IAC counts preferably around 30 but lower is better.
A scanner connected to the OBD1 port should show these values in real-time for you. CSI you'd have to pull a fuse for.
Do you get a SES light on when you start up and it's cold out? If so, does it go away on it's own as the engine starts warming up and the engine smooth out around the same time? Do you not get any codes when this happens, and does it seem like it only happens when it's cold out?
That's the symptoms I had with my 86, only seems to happen when it's colder out. One thing you can try, rap the IAC valve with something like a plastic faced hammer or screwdriver before attempting to start and see if it changes anything. In my case, I changed out the IAC and OS2 sensor (which also needed changing) and my problem went away.
Do you get a SES light on when you start up and it's cold out? If so, does it go away on it's own as the engine starts warming up and the engine smooth out around the same time? Do you not get any codes when this happens, and does it seem like it only happens when it's cold out?
That's the symptoms I had with my 86, only seems to happen when it's colder out. One thing you can try, rap the IAC valve with something like a plastic faced hammer or screwdriver before attempting to start and see if it changes anything. In my case, I changed out the IAC and OS2 sensor (which also needed changing) and my problem went away.
Good luck
NO SES light. Also I was too quick declaring it was fixed ... when I tested it for the second time it was 70s out and it ran OK but this morning it was 40s and it was awful.
To be specific it would miss and sputter below 1000 RPM but when I revved it the miss would go away until I warmed it up ~120.
Recent spark plugs, rotor & cap, IAC, O2 sensor and CTS.
:will y:
It may be the fuse to the cold start injector ... I'll let you know.
Last edited by 3D-Aircrew; Nov 14, 2019 at 01:11 PM.
My injector fuses are good. I've been reading the FSM about what's called the "cold start valve". It depends upon a thing called the "Thermo time switch" which is supposed to open the cold start valve when the engine is cold. Is the "cold start valve" another fuel injector that simply is turned full on when the engine is cold? Where is the auxiliary fuse box located?
Last edited by 3D-Aircrew; Nov 15, 2019 at 01:07 PM.
Yes the CSI is on the fuse labeled CRANK. Pull that fuse and it doesn't work. That is the fuse I was referring to above. Noid lights are all you need to check the others.
Aux fuses on my 88 are behind the center dash, behind where the switch panel is.
My 88 L98 had cold running issues, no Codes... was a bad MAF.
Are you connecting to the ECM with anything to read values from the ECM? If not, you will just end up swapping parts until you find the correct one.
KyleF;
I used to have some MAF and IAC issues but I corrected by changing the relays and IAC. The only reason changed the CTS is because the connector on the valve broke when disconnecting to test. This is a 33 year old car and the parts are brittle.
I used to have tuner pro and a Bluetooth adapter to communicate with the ECM but that laptop died and I just haven't been able to sort out the files I need and reinstall tunerpro yet. That would certainly help but I remember when I did have it working that the 165 ECM is DOG SLOW at 1Hz update rate. I've had others tell me that I should upgrade the ECM to the 1987 which is much faster.
The 165 ecm supports both 160 baud and 8192 baud scanning, however 1986 is a special case due to differences in the serial data initialization programming compared to the later 87-88 and 89 bins.
Diacom users have long reported success scanning 86 cars at 8192 baud. I've successfully scanned stock 86 bins at 8192 baud with DataCat. I've even re-written a few 86 bins to allow 8192 baud scanning with TunerPro, but I could never get a stock 86 bin to connect at 8192 baud with TunerPro no matter what I tried with various *.adx file programming changes.
Bottom line: it really depends upon the scan tool. My suggestion is to try DataCat first since it has been proven to work.
Thanks for the encouragement and suggestions. Well I got a different laptop and installed Tunerpro RT just like last time. I have a Bluetooth interface that's not connecting. I was able to connect my phone to my laptop with Bluetooth but I can't get the laptop to see the the Bluetooth interface. IDK why I bought the BT adapter in the first place when a straight cable would have done the trick. It has extra cable and a power connection. Now I have to deal with a flaky power connection to the cigar lighter but even when the BT adapter is powered it won't connect.
The Tunerpro RT is working great though and I was able to load old setup files from before.
Last edited by 3D-Aircrew; Nov 22, 2019 at 04:13 PM.
Cold Starting Problems - Won't idle, sputters 1986 Vert
Thanks for the advice
