1989 idle humbs and 1500rpm hesitation
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Author:  Karpov [ Thu Jan 18, 2018 3:29 pm ]
Post subject:  1989 idle humbs and 1500rpm hesitation

Check last pages.


Author:  96 SSEi [ Thu Jan 18, 2018 5:35 pm ]
Post subject:  Re: 1989 and hard cold start

hi, since its new, maybe start with plugs/ wires, air/fuel filters - easy enough and not too expensive

you can clean throttle body - pretty sure your car is fuel injected so maybe some fuel cleaner to add to gas.

see how it runs after you check/change/clean..............

Author:  Karpov [ Thu Jan 18, 2018 6:02 pm ]
Post subject:  Re: 1989 and hard cold start


Plugs and wires pretty new. Ill check filters.

Yes its original mpfi.

It pops in exhaust maybe one time per minute/two. Not often but ...

30mph is slight hesitation in slight throttle. Ex owner said that one appeared when maf were replaced.

Author:  96 SSEi [ Thu Jan 18, 2018 6:15 pm ]
Post subject:  Re: 1989 and hard cold start

so you have no codes? check engine light is off? I would check the plugs and wires just for fun.

Maf, yes you can clean that also - maybe grubby, dirty hands were touching it. you can try unplugging it and see if it starts and runs better.

Author:  Karpov [ Fri Jan 19, 2018 5:29 am ]
Post subject:  Re: 1989 and hard cold start

Thanks. No ses but ill check if stored codes.

Author:  Karpov [ Sat Jan 20, 2018 5:12 am ]
Post subject:  Re: 1989 and hard cold start

I order new plugs and wires and get them in two weeks.

Now in hot engine, after 15-30min stop when you start, idle humps 500-1000rpm. When you give throttle it calms.

Author:  96 SSEi [ Sat Jan 20, 2018 9:43 am ]
Post subject:  Re: 1989 and hard cold start

you can clean the IAC - see if idle improves
if the engine is cold, it should climb to high idle and slowly come down - I woul clean the iac and throttlebody - just get throttle/carb cleaner and spray and wipe
Dont run the engine and spray it in the throttlebody - you will kill your cat !!!

take off all the sensors from throttlebody and clean everything - then do the TB - let it sit for 5 min, reassemble and your good - be careful of vacuum lines - they get old, hard and break.

you dont have a location in left margin, are you in Europe? if you have 20% or more ethanol in your gas, the system should be nice and clean.

Author:  MKMike [ Sun Jan 21, 2018 12:09 pm ]
Post subject:  Re: 1989 and hard cold start

Is the check engine light on?
Does the check engine light come on when you turn the key to the ACC position or is the bulb burned out?
Some big chain auto repair shops will read the computer codes for free.
The codes can offer clues as to what the problem is.

Since the problem started with a replacement MAF that replacement sensor is defective or, if obtained from a junkyard, it may just be dirty.
You can clean the sensor using a spray can of special MAF Sensor Cleaner.
Other cleaners leave a sticky residue that attracts dirt--making the problem reappear in a short time.
There are 2 thin wires inside the MAF sensor which the computer uses to calculate how much air is entering the engine.

Rockauto lists a brand new MAF sensor from Cardone Select for about 110--cheaper, if you use the discount code (see their Pontiac Bonneville Club Vendor's forum post).
There are also ACDelco Remanufactured units available, but at around 2x the cost.
Ebay, if the seller is reliable or a junkyard that offers a warranty are additional options.
Of course, you'll need to clean any used MAF that you get.
You want to be sure the replacement part has AFH50M-02A embossed in the part that bolts onto the MAF sensor housing when buying used.

One maintenance item to not overlook is the PCV valve.
A stuck open PCV valve will cause hard starting.
ACDelco PCV valves work best in these cars.

If your spark plugs are Bosch, I strongly advise replacing them with ACDelco, NGK, Autolite or Champion.
For whatever reason, Bosch spark plugs have proven to be problematic in Bonnevilles.

You can also try a tankful at another gas station if you always buy from the same one.

This is the forums's Care and Feeding Maintenance list

Author:  Karpov [ Sun Jan 21, 2018 4:35 pm ]
Post subject:  Re: 1989 and hard cold start

Thanks for tips again.

Yes i live europe but i use ethanol free gas. Different type gas doesnt efect.

Can i clean iac with carb spray? I got tbi pickup and they said dont clean iac with carb cleaner it will ruin it?

How about maf, will oxide clean/electronic spray be fine? Maf change and problem is ex owners word only.

I start car tomorrow, then its been 3 days since last start. Because overnight standing did not make poor cold start.

I ordered autolite plugs. That gap what rockauto said is big at my mind? Shorter gap will help ignition system and long gap needs more power? This has original style one big coil. If it brokes i will replace icm and coil that never version.

Check engine light works acc mode and goes away.

Author:  MKMike [ Sun Jan 21, 2018 10:20 pm ]
Post subject:  Re: 1989 and hard cold start

Rockauto didn't decide on the 0.60 inch spark plug gap---the engineers at Pontiac determined that that was the best gap to combust the fuel.
You can read about the rationale for the gaps here:
http://www.ngksparkplugs.com/about-ngk/ ... d-indexing

The problem with discussions is that the cleaning chemicals available in the US are often unavailable in Europe--or are called something unfamiliar.
The US market carburetor cleaners are often too strong for cleaning throttle body parts, as they melt plastics, are incompatible with certain metals and may remove protective platings.
If you were told that carb cleaner will ruin the IAC, I would trust them and look for a compatible cleaner.
For the IAC and throttle body, a popular cleaner in the US is CRC Throttle Body and Air Intake Cleaner, which is mostly acetone--as can be seen on this Material Safety Data Sheet

For the MAF, you can use surgical spirit (called rubbing alcohol which can be ethyl alcohol (ethanol) or isopropyl alcohol in the US).
This article indicates that electrical contact cleaner may be OK IF it leaves no residue.
Personally, I'd use the ethanol and a cotton swab.

The forum instructions for MAF and throttle body cleaning are here:

I wouldn't remove the throttle body, since it requires a new gasket--though it does ensure the most thorough cleaning possible.

Author:  Karpov [ Mon Jan 22, 2018 5:43 pm ]
Post subject:  Re: 1989 and hard cold start

Thanks. Then i use electrospray for iac and maf. And use 0.6 gap.

Today -25 celcius and about 3sec start snd car was running fine.

At first big problem start i had 1/4 fuel in tank. So maybe fuel pump caused that horrible long start?

But now its only 3sec, still its not that nice that i wanted

Does bonneville have fuel pump door inside or is it fuel tank off and then get the pump out?

And motorad offers high flow thermostat, is it better than normal? They promised faster engine warm up in cold, thats what im interested.

Author:  MKMike [ Mon Jan 22, 2018 9:36 pm ]
Post subject:  Re: 1989 and hard cold start

If the electrospray doesn't leave a "protective" residue on parts, then it should be ok.

The PCV valve can cause hard starting and rough engine performance, especially when cold.
If the fuel filter is very dirty, that could be the problem.

When a car is new to you, you are wise to replace all of these maintenance parts first.

Check all of the vacuum hoses to be sure none have cracked or broken.

Also examine the hoses at the charcoal canister/purge canister/EVAP canister--assuming it has one.

There should be an underhood sticker showing the location of all vacuum hoses.

Before changing the fuel pump, I would measure fuel pressure to be certain that the fuel pressure regulator is working well.

I am not certain about your 89 but my 93 Bonneville and 98 Bonneville had no access door for the fuel pump.

Sorry, but I am not familiar with how high flow thermostats do or don't affect warm up.

If you mean that you want the heat inside the car to be better, then make sure you have the right temperature thermostat AND you can back flush the heater core.
Back flushing the heater core involves disconnecting the heater hoses and forcing water or a cleaning solution through the heater core in the opposite direction than it normally flows.
This removes deposits that built up inside the heater core, allowing coolant to flow better through it.

If you are able to, parking the car overnight inside a garage or other enclosed area will promote faster warm up.

Author:  Karpov [ Tue Jan 23, 2018 4:45 am ]
Post subject:  Re: 1989 and hard cold start

Yes thanks.

Car warms wery well, upper radiator hose is hot too. Gauge only shows 2/6 part of temp but ill check today hose degree. Maybe gauge is bad or i have 180f etc thermostat.

New pcv and fuel filter is also coming. Fuel filter is under car like many other?

I have fuel pressure gauge, maybe i have even correct hose fitting for fuel rail :)

I dont have garage etc so must wait until weather is warmee, before i try crack vacuum hoses and their plastic pipes hehe.

Author:  96 SSEi [ Tue Jan 23, 2018 11:30 am ]
Post subject:  Re: 1989 and hard cold start

YES, fuel filter is on the fuel rail near the back doors/ tank - you look and you will see the silver,metal canister.

fuel pump is in the tank - have to drop it -dont buy pump for no reason - do the other common stuff first and then if the pressure is still low, you can look at the pump.

pretty sure your issue is not mainly pump.

i hope you mean .060 inch for plug gap - .6 is way too large

Author:  Karpov [ Tue Jan 23, 2018 12:08 pm ]
Post subject:  Re: 1989 and hard cold start

Yes .060 heh. I have good gapper with inhces so thats gonna be easy.

No fault codes i just checked.

Car was in engine heater about 40minutes and started better than never before, just show the key. Even full warm engine it has not started so well. It starts pretty well when engine is hot/warm but it has one second delay.

Near to perfect but not full perfect if you know what i mean :)

Car sleeped overnight before that start so me too wont believe fuel pressure problem. Had a volvo with weak pressure some years ago, and days first start was allways hard no matter outside or engine temp.

Author:  96 SSEi [ Tue Jan 23, 2018 5:54 pm ]
Post subject:  Re: 1989 and hard cold start

good!!, you see, diagnose first, dont throw parts at it.

she will run great after plugs/wires - you may get better fuel economy as a bonus!!

Author:  Karpov [ Wed Jan 24, 2018 3:38 pm ]
Post subject:  Re: 1989 and hard cold start

New 195f thermostat is on its way.

With infrared it gived now only +-180f engine temp so it has 180f i think. Too cold in here.

Author:  Karpov [ Thu Feb 08, 2018 6:28 am ]
Post subject:  Re: 1989 and hard cold start + other problems

I edit headline because i dont want open more topics.

Ex owner said that car did 3-5 times on past 10 years that: when you engage transmission d it wont move before you switch it p or neutral and again d. In hot engine.

Now it did that but on crossing road! So i came about 30mph and slowed down for other cars, then pressed pedal mut no movement. P and back to drive - all fine.

Some kind of seal is leaking pressure? This wont sound nice or easy to me :(

Trans has fluid and color and smell fine.

Author:  Karpov [ Thu Feb 08, 2018 8:10 am ]
Post subject:  Re: 1989 and hard cold start + other problems like transmiss

And can tranny be removed upper side without engine?

Author:  Karpov [ Fri Feb 09, 2018 1:18 pm ]
Post subject:  Re: 1989 and hard cold start + other problems like transmiss

Trans manual said that after low fluid level and pressure, sympton can be 1-2 piston+valve which is located firewall side on trans.


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