1988 Beretta GT Rough idle when "cold"

[zcylex]

Hi everyone,

New member here though i've been reading this forum since i brought this car a few months ago, so heres the story.

this is 1988 beretta gt coupe 2.8L v6 belonged to my grandad and recently my dad brought it for me and him(to help him out)
so my dad and i have this project to get it fixed and bring it back to its glory days. the problem comes when starting the car, in the morning, afternoon, night whatever the time we start it for the first time in a day the car days and i have to push it to about 4k rpm to keep it running otherwise it shuts off, SES light shows error 53 which could be system voltage or EGR.

all the sensors in the car are new, installed them yesterday, i changed MAF, IACV,TPS and the EGR valve plus i brought the crankshaft position sensor though i have installed it yet. im very suspicious about the battery since its old however the car always had this problem. recently took it to a local repair shop where it was checked for "everything" (though in my country thats not much as i leave in Honduras and we're a lot behind in tech and all that) anyways the mechanic said everything about sensors is in working order so it shouldn't be giving me any issues.

now the weird part is that when i get it to "normal" working temperature after about 5 to 10 minutes of "heating it up" the car runs fine i can turn it off and it works great all day, aside from terrible mpg (about 13-16 mpg) though i leave in a very hot weather.

hope some of you experts might help me(us) in finding the solution for this, thanks in advance.

[ifixalot]

How many miles on the car?
Are you loosing coolant?
Any bubbles in the coolant when the engine is running?
Have you ever pulled the plugs? Do they look OK or is one or more black? (you can search for what they should look like)
How are the plug wires? Then there is the ignition module and coils. Reading the plugs can point you to which cylinder is mis-firing.

[bagged_and_loud]

Is it a 5 speed?

[zcylex]

Wow thats a lot of questions lol ill try to respond them all at my best,

I dont know how much miles does it have since odometer's been dead for quite a while now but i know its a lot of miles in the car since the previous owner brought it from texas DRIVING IT!

Yes i am loosing colant and theres a few bubles coming like every second with the car running

The plugs are fine though i have to check the coils and the ignition module you mention.. And as i stated earlier this only happens when the car is cold, meaning first start in the morning, otherwise it works fine.

I do not know if it is a 5 speed, its a 1988 beretta gt coupe with a v6 2.8L automatic transmission

Thanks in advance

EDIT: it has 103k miles o it, spark plugs and wires are 3 month new, and i've been researching and sounds like it could be the coolant temp sensor does anyone know wheres that located?

[Rettax3]

Look under the throttle-body, in the lower intake manifold for the coolant temperature sensor, right near the thermostat housing, near where the upper radiator hose connects to the engine.

Bubbles in the coolant might mean a blown head gasket. Your 2.8 engine has much stronger lower intake manifold gaskets (LIMGs) than the later 3100 V-6s do, and it is not notorious for failure there, but that could still be a problem.

You do NOT have a five-speed transmission if you have the automatic.

Does your car have a roundish air-cleaner box and a mass air-flow sensor? I think it probably does. Chevy offered a computer update for that engine that changed it to speed-density (MAP, or Manifold Absolute Pressure sensor) instead of MAF, and the MAF was only used as an intake air temperature sensor after that upgrade was accomplished, as I recall. Look around on the engine and under the hood for some sticker identifying that your car has gotten the update, otherwise you could be experiencing problems with the MAF or the computer. I don't know if you can still get that update installed at a dealership, I rather doubt it.

Welcome to the site, we would love to see some pictures! Good luck.

[zcylex]

My car doesnt have the speed density update and i do have the MAF sensor, i read in a site about making the upgrade myself by changing the maf for an IAT and the ECM PROM from an 89-90.

The so called mechanics here had performed dumb repairs making more harm than good (like leaving the cooling fan always on etc.) they disconnected the heater core pipes and just sealed them away, weve found the vacuum hose to be loose from the main vacuum and a missing "outside air temperature sensor" which is supposed to be in the from of the car in front of the radiator, i found the conector and terminal but the sensor was cut off and is now gone.

The coolant temp sensor is wokring correctly as i tested it, now im looking at the alldatadiy manuals for the car i brought the suscription yesterday and i hve found a lot of useful information in helping me understanding how the car really works and what has been "adapted" by local mechanics.

The problem loosing coolant appears to be gone but when the car is running theres one bubble coming from the pipe at the bottom of the coollant container, although my dad says its gone now....

About the pictures i will upload them as soon as i get past the 5 post new member limit(which really frustrates me but is the forum rules i have to respect them, i have managed a few forums in my life and i understand the reasons, though i dont like it lol)

[Rettax3]

It sounds like you are on the right track with your car. Good luck with it.

[zcylex]

Ok so i've hit a dead end.

This is what ive done so far:
-replaced the battery for a new one
-took the alternator for a check , replaced regulator the rest is ok
-replaced maf, iacv, egr, cps, o2, tps
-checked coolant temp sensor and is fine
- redid grounding on alt, batt.
- repaired atleast 3 or 4 vaccum hoses
-checked all spark plugs and wires all fine

The current dtc codes are:

23 "mat sensor" which is in the maf and the maf is new
35 "iacv" which is also new
53 "high voltage or egr" solved it when redid grounding then came back
63 "low vaccum" points me to the map sensor which i havent replaced but the error is intermittent

I have fixed all that ive found and all i get is minor improvements but the same problems

When starting the car in cold it stalls and i got to keep it around 3-4k rpm to keep it running until it warms up then it stabilizes

What to do now?

[3X00-Modified]

Ohm check the wires from the MAF MAP and EGR to the ECU to see if they are shorting out somewhere. It sounds like it's either a bad wire in the harness in those areas, a bad ground, or bad connections at the ECU... Check for corrosion at those points where it plugs in.

There are a bunch of wires that come out of the harness at various locations which provide the sensor grounds and such, so you need to find those and make sure they are connected good.

[zcylex]

did that with a mechanic a friend recommend (its hard to find mechanics here that know about efi, without screwing things up that is) anyways we ohm check and all was good, removed iacv and he "regulated idle air with his finger" and it helped the car a lot, so he said something must be wrong with the ECM that is not regulating iacv correctly. took out the ecm and found some damage where the IACV cable connects (i have all the diagrams for the car and will be uploading them to this fine forum later ). he then took us to a guy who supposedly fixed ECM ( i thought i give it a shot before ordering a new one since it takes 2 weeks to get here) so well see what happens.

on a side note, does anyone know where i can get the PROM from an 89-90 beretta in the us? to make the speed density update myself. the problem is that in my country the berettas were never really sold and it makes a rare piece in here lol. i've seen only one in the country and none in my city. also does the alphanumeric code on the PROM/ECM matter when doing this update? mines "AMAL" no quotes. i read somewhere that the number do matter so i have my doubts.

[ifixalot]

I asked about coolant loss and bubbles because you may have a leaky head gasket.
When the engine is warm, the pressure in the cooling system forces coolant into the cylinder's combustion chamber.
The warn engine can evaporate the small amount away the compression keeps the coolant out and/or maybe the gasket seals when warm.
But when you shut it off at night coolant leaks into one or more cylinders and wets those plugs and they won't fire. After awhile the plugs dry out.
As the engine warms up, the problem corrects itself.
Try this, after the engine is warm and running good, when you shut it off for the day, slowly loosen the cooling system cap until the pressure
escapes. Leave it like this until the next day and see how it runs.
If it starts and runs good the next day, you have a head gasket leaking over night and wetting your plugs.
My daughter's car had this when her head gasket was leaking. In addition, her OBD2 was throwing a code for a bad rear oxygen sensor.
Your codes could be related to misfires in the engine until it warms up.
Now if it look like a bad head gasket, that is an expensive repair. You could try one the many bottled fixes, they work but only for maybe a couple years.
Aluminum heads can corrode if the coolant hasn't been changed often enough which can cause a failure.

[zcylex]

Coolant leaks are minimal and the bubbles only appeared once then i never had them again the head gasket would be my next check but i have to wait till my ecm is either repaired or replaced by the new one thats why i asked for directions regarding the speed density update so i can order both the ecm and the prom at the same time with the new iat sensor too and get that mod done once and for all.

I still have a long way to go with the car as im just startin here but any help along the way would be much apreciated

[zcylex]

got the ecm back, the guy didnt have time to fix it so ill have to wait atleast until monday.

however, in the alldata manual i found a tech service bulletin which points to a manufacturing defect and not the sensors or the iacv. now how do fix this are prom replaceble? found some on ebay but dont know which to buy.. i dont know if they have to be programmed individually for my car via VIN or something or is there anything i can do to change my prom and ECM ?

anyone here has replaced the PROM? I CAN GET the same ECM but i dont want to get the same prom and have the same problems months or years from now.


PS if someone need any info for the 88 2.8L V6 model with VIN W i can upload whatever i can find in the alldata at least until my suscription lasts lol.. i can't upload all cause its a lot of stuff...

[3X00-Modified]

What is the service bulletin referring to as a manufacturing defect?

The ECM can be any that matches the last 4 digits of the service number on yours, and the prom you just need one that is the same engine/trans/year combo. And if you can find it you can go with the speed density upgraded prom and eliminate the MAF sensor.

[zcylex]

heres the TSB content theres a few steps, and in step #7 it says replace MEMCAL

Number: 88-88-6E
Section: 6E
Date: NOV., 1987
Subject: ENGINE STALL AFTER HOT RESTART/COLDSTART, AND COLD ENGINE HESITATION
Model and Year: 1987 CAVALIER, CELEBRITY WITH 2.8L (VIN W) ENGINE 1987-88 BERETTA, CORSICA WITH 2.8L (VIN W) ENGINE
TO: ALL CHEVROLET DEALERS
Some 1987-88 models listed above, equipped with a 2.8L V-6 engine, may experience a cold start stall, a stall after start with a warmed-up engine or a stall during deceleration. A 5-speed manual transmission Beretta, Corsica, or Cavalier may also experience a hesitation during acceleration, primarily when the engine is cold (ambient temperatures of 40 to 70 degrees Fahrenheit). This hesitation may also be experienced during transmission gear shifts.
A repeated stall after hot restart may be caused by residue accumulating inside the throttle body bore behind the throttle plate, which limits the air flow past the throttle plate in the idle position. The hesitation concern may be due to a lean Electronic Control Module (ECM) fuel calibration. The cold start/stall may be due to a lean ECM calibration, low engine idle speeds, loss of fuel pressure, or loose electrical connections at the ignition coil and/or the mass airflow sensor.
The aforementioned customer comments may be repaired as follows:
1. Perform normal service procedures as outlined in the shop manual for the repair of engine stall or hesitation.
2. Verify that all electrical connections at the ignition coil and mass airflow sensor are secure.
NOTICE: LOOSE/POOR ELECTRICAL CONNECTIONS AT ALL SENSORS AND ECM METRI-PAK CONNECTORS CAN BE A PROBLEM ANYWHERE ON THE ENGINE. INTERMITTENT CONNECTION CAN PRODUCE STALLING.
3. Verify that there are no engine vacuum leaks at the manifold absolute pressure (MAP) sensor, positive crankcase ventilation (PCV) valve, exhaust gas recirculation (EGR), or other systems.
4. Verify that the fuel system is functioning properly and has proper fuel pressure. Reference Chevrolet Dealer Service Bulletin 87-83 (Section 6C) dated March 1987.
5. Clean the throttle body bore as specified in Chevrolet Dealer Service Bulletin 87-109R (Section 6E) dated May 1987.
6. Measure the minimum idle speed and throttle position, and adjust to specification if required (reference Chevrolet Dealer Service Bulletin 87-109 Reissue.
7. Replace the ECM MEMCAL (see Attachment A), using the following installation procedure:
(a) Disconnect battery power.
(b) Install new ECM MEMCAL calibration.
(c) Reconnect battery power.
(d) Start vehicle with AC/defroster off and power steering not cramped.
(e) Allow vehicle to idle in drive for 6 minutes and until thermostat has opened. This will facilitate learning of base idle.
(f) Return vehicle to service.
NOTICE: IT IS INAPPROPRIATE TO REPLACE THE MEMCAL AND RETURN THE VEHICLE TO THE CUSTOMER WITHOUT PROPERLY COMPLETING THE PREVIOUS SERVICE INSTRUCTIONS (ITEMS 1-6).
Use applicable labor time and operation numbers.

im getting the same ECM PART NO. 1227730 and about the PROM which one or where could i get one like the one you mention?