RS-Chevy-SS

----UPDATE CHANGED PARTS LIST----
MAT SENSOR
02 SENSOR IN EXHAUST

89 rs 305 tbi Okay heres what it does....after u drive it and it heats to 220 and u park it and let it sit for about 20 mins if u try to restart it....it will start and idle at 1000 then drop to 300 then go back up and drop again....but the thing is that it doesnt do that when its cold...any ideas? ill post sum vids later on today...

VIDEOS
Idling:

http://myspacetv.com/index.cfm?fusea...deoid=17208272

RS-Chevy-SS

Bump!!

RS-Chevy-SS

ANOTHER BUMP!!! Need some help guys

RFmaster

Regulator

I did not watch video - I'am on the road. Check for a stuck thermostat, you should not be running above 100C while idling. Once you get this hot (100C+) ECM will lean out engine, while increasing idle speed. A very lean hot engine will do chicken dance and IAC may not have range to adjust for it. Also, get a Lappy and WinALDL with ALDL cable - collect engine performance data while trouble shooting.

//RF

RS-Chevy-SS

Im thinking about doing the paper clip trick today........But the thermastat is a 160

RS-Chevy-SS

Okay so i just ordered the MAT sensor today...Hopefully that fixes it

RS-Chevy-SS

Okay I just put the damn sensor in and it helped a lil bit but it still does it...Whats next???

acescarrsRS

I had a similar problem with my car a while back. Damn idle bounced all over the place. Mine was a combination of bad sensors & bad distributor. I'll go do some digging on my past posts when I had the problem to see if I can help. Hope you solve your problem!

kuulkatdadieo

iTrader: (1)

o2 sensor maybe.

RS-Chevy-SS

I was thinking about maybe testing the coolant temp sensor next....

RFmaster

Regulator
Temp Sensor is a simple resistor with a inverse temperature characteristic. Get a DVM, disconnect harness, measure resistance. At room temperature (22C), cold engine, resistance value should read at about 2650 to 2700 Ohms. Typically temperature variation is a slow moving process compared to dizzy reference signal or O2 sensor voltage swing.

To get to the bottom of this get WinALDL/ALDL cable/lappy and get extensive data log. With engine cold, start to record all parameters and post this log here. Otherwise, you will be spending money on sensors blindly.

//RF

RS-Chevy-SS

True...My friend is to let me borrow his scanner soon....But there isnt any trouble codes lite right now....

RFmaster

Regulator

That's the problem with early OBD-1 systems. They were really designed to detect when things went totally amok or missing. An extensive data log will tell you what is marginal and causes a detuned condition. Scanner will give you a short time period snapshot. When trouble shooting a 'weird' problem it is best to have the whole picture.
//RF

dimented24x7

iTrader: (2)

220 is normal, regardless of what T-stat is in use. Unless teh fan switch has been changed out, itll idle at around 220-230 degrees.

RS-Chevy-SS

Ok where can I get this aldl cable at? And also were can i get this program....Actually a step by step explanation would be good

RFmaster

For ready made ALDL cable

http://www.aldlcable.com/
Select appropriate type depending on available port (RS-232 or USB) on your lappy. You can find them EBAY as well.

For WinALDL - http://winaldl.joby.se/

Verify the ECM service number that you have in your '89. ECM should have a label on its cover. In most likelihood you have 1228747 which was used with TBI LO3 engines. There is also broadcast code (BCC) on the same label.
In WinALDL under com port speed set it up for 4800 baud (default is 2400 which does not work). You can perform data capture - record all parameters, all flags.

//RF

RS-Chevy-SS

Ok thanks...So when should I be recording the data? What should i be looking for?

RFmaster

Regulator

In WinALDL select your ECM type (now you know why asked which one you car is equipped with!). Set Com port to the port that your cable is hooked up. You will probably have questions regarding com ports - ask away when you get ALDL cable and WinALDL loaded into your lappy.

In Data logging window select all options: RAW Data, Sensor data, Flag Data, and Error Codes. The only limit for how long you can log is the available disk space. I think within 10 to 15 minutes your engine should warm up to operating temperature and exhibit the funky idle. The data log file will have data organized in columns, while each row is time snapshot.

How to start data log - assuming that all software and cable issues have been ironed out. Connect ALDL cable to vehicle ALDL port, lappy is running WinALDL with properly selected ECM. Place key into run position, but do not start yet - you should RAW data stream from ECM. Switch to Sensor data tab and you should see reasonable data for a cold engine. IAT should be close to ambient temperature, coolant temperature should also be something reasonable. TPS should be around 0.5Vdc. You get the drift.

Start engine. You should see RPM's climb to cold idle, IAC counts vary, battery voltage increase from 12 volts to 13.8, etc.

Let it run on its own until it starts acting up. If possible record at least 5 minutes of it. After 5 minutes gently bring engine to 2000 RPMS for about 30 seconds, than bring it back to idle again. Record another 2 minutes of funky idle. Shut engine off, exit datalogger. Data logger file will stored in the same directory as WinALDL and will have a date and time in its file name. It is flat text file which can be readily imported into excel for analysis. Now you have a very detailed map of your engine operating parameters.

//RF

RS-Chevy-SS

But here is the only issue it only acts like that after if warms up to 220 and you let it sit for 20 minutes then try to start it again....So do i still need to record when its cold?

RFmaster

Do both - the more operational data you have easier it is to debug.

//RF

RS-Chevy-SS

I was talking to one of my mechanic friends and he said it sounded like a bad fuel pressure regulator....Any way to test this part alone? Without the lappy?

RFmaster

Yes - you can. You can rent fuel pressure tester from Autozone. Do a search here for a test procedure. There is a sticky on TGO how to test TBI pressure regulator. Sometimes, spring will break in the TBI PR. It is very easy to replace TB PR, complete repair kit is about <$30 from most auto parts stores.

//RF

RS-Chevy-SS

Ok kool...I havent gotten the stuff yet..But I did flash the code today which was 44....Which is 02 censor reads lean....I just bought the new sensor right now and replaced it ...Wish me luck

RS-Chevy-SS

Ok so that didnt work....Damn im starting to get P.O ed

RFmaster

Before getting P.O. Verify fuel pressure - changing sensors blindly will get you no where fast. With WinALDL you can see what engine sensors are doing when she is miss behaving...

//RF

RS-Chevy-SS

Ok thanks bro I think the next thing that im going to do is buy a fuel pressure tester and see how the pressur looks...My mechanic told me it sounded like a bad fuel pressure regulator but I asked him if it was that why is it that if you just let it cool down for 2 hours and then started it up it would start up and idle fine? he didnt have an answer....Its a toss up with whether I wanna get the aldl cable or the test....If i can find a cheaper cable then the one you showed me then ill prolly lean towards the cable.....

RFmaster

Regulator

You can rent fuel pressure tester (FPT) from autozone or other auto parts store. There is no test port on TBI. Testing FP on TBI involves bolting in a T junction right at the TB inlet port. Other place where FPT can be inserted is by fuel filter

A typical pressure regulator uses a spring of some sort to control fuel pressure. Over time spring metal gets tired and with age its properties change. So a spring may get weaker as it get hot. Engine gets hot, fuel pressure goes down. You get a picture!

TBI rebuild kit is about $30 from most parts stores - you get everything, gasket, spring, etc. Take a look before pick it up - I've one, let me take a look.

There was a post awhile back - gent took his FPR spring out. It was broken in three pieces.

FPR is an easy overhaul - just make sure that you use double wrenches when unbolting supply and return lines from TB pod. Also, you'll need TORX drivers.

//RF

BMmonteSS

It's most likely the fuel pump, pumps work better when they are cold. Once they warm up a bit they tend to slow down and not want to get moving again once you shut them off. I wouldn't replace it untill you verify that the fuel pressure is indeed off.

RS-Chevy-SS

So if I do see a definate drop in pressure whats to say that it isnt just the pressure regulator and not the fuel pump?

RS-Chevy-SS

Also is it possible for the FPR to leak into the motor after shutdown?

BMmonteSS

In my experience regulators only fail in two ways, they will either leak (you'll find fuel between the TB and the dissy) or the spring breaks which means you'll never get any fuel pressure and the motor won't run.

Considering that the fuel pump goes out about 20 times as often as guys have problems with regulators.....I'll place my money on the pump. No need to guess, just get a guage on it and quite guessing.

RS-Chevy-SS

When i put the gauge to it...Is there anything that will tell me if it is the reg or the pump?

RFmaster

Regulator

If you install pressure tester in place of fuel filter you can perform a 'dead head' test. By pinching off or severely restricting fuel flow after pressure tester you should see immediate rise in pressure. If not FP is history and its time to drop a tank.

With normally functioning fuel pressure regulator you should see 10 to 14 PSI without any pinching of lines, etc.

//RF

RS-Chevy-SS

No!! I dont wanna drop the tank again! Ive already done it 3 times in the past!!! But ok and if its not the Fuel pressure then whats next?

RFmaster

Regulator
Ok, Ok - I hate dropping tanks as well, who can blame you! That's why verifying all is well with fuel flow is the key (without dropping tank). By verifying fuel pressure you check off fault cause on a troubleshooting tree.

Moving forward - getting back to my earlier post - WinALDL monitoring sensor action during 300 rpm to 1000 rpm hot idle cycling is a low cost approach. Before, starting with WinALDL - check usual suspects, clean IAC and reset IAC. Do a search here - there is a step by step procedure how to do that.
Check for leaky gasket between TB and manifold
Check all vac hoses for cracks and softness - you know the drill.
Put a DVM on alternator +B terminal - make sure that gives you nice steady 13.5+ volt output. Alternators are know to die with heat and put out crappy AC ripple on DC bus which can cause havoc with ECM and sensor readings.

What bugs me is that a hot soak is required for this idle oscillation to take place.

//RF

RS-Chevy-SS

Yeah thats the thing that troubled me to!! Its only does it after a 20 min heat soak...You can check the alternator off the list because its brand new and i just checked it last week.... Also disconnected the IAC removed it cleaned it and put it back in...

RS-Chevy-SS

Ok so....Today I decided to clear the ecm completely....I disconnected the negative battery cable for 2 mins reconnected...Flashed the trouble codes and only 12 showed up...So clear right? Also With the cable connected again I disconnected the iac valve wiring with the engine off for about 10 secs then reconnected it....Does this reset it?

RFmaster

Regulator

Code 12 is all good....

IAC
1. Warm the engine to normal operating temperature.
2. To fully extend the IAC, jumper ALDL pins A and B together, and turn the key on, but do not start the engine. With the key on, engine not running, and in diagnostics mode, the ECM will keep trying to fully extend the IAC.
3. After 10 seconds or so, pull the IAC connector off the IAC before doing anything else. This will remove ECM control over IAC while its fully extended.
4. Now pull out the jumper in the ALDL, and start the car. Typically the "minimum air" idle speed is in the 400 to 500 RPM range, so you may need the manual for the spec for your model year and engine. Set the idle to spec using the throttle stop screw. (The engine should be fully warm to do this.)
5. Now shut the engine off and reconnect the IAC connector.
6. The ECM does not 'know' where the IAC present position is, so pull the ECM fuse or negative battery cable for 20-30 seconds. (This will cause a complete ECM reset.)
7. Reinstall the ECM fuse (or negative cable).
8. Turn the key on, wait 10 seconds or so, and turn the key back off. This will now reset the IAC to a known key-off "park" position.

Voilà

//RF

RS-Chevy-SS

Is this a must? Also Its starting to throw that 44 code every day now...Its getting steadily worse every day

RS-Chevy-SS

BUMP!!! URGENT! I just go the ok from the manager of autozone to try out a new map sensor and IAC for free but only one at a time! Which should i try??

BMmonteSS

I'm sorry man but there really isn't much more we can do untill you do some diagnostics work. If your map sensor was bad you wouldn't make it out of the driveway and if your IAC was bad you would just have a high or low idle.

RS-Chevy-SS

Ok thanks bro...Here is what I did....I changed the map sensor and it seemed to greatly improve the condition...Unfortunately it was too late for me to accurately test the condition due to the fact that its hard for the car to heat up with a 160 stat and a fan wired to continously run...when it is night outside and its starting to cool down.....Tomarrow is the real test...Wish Me luck!!

UPDATE--- You can forget about that...It didnt completely fix it...But it did improve it slightly....

RFmaster

regulator

If you had WinALDL and cable you would have seen that MAP sensor is reading too high at idle, for example. Also, having 160 F thermostat and fans blasting would keep ECM from going into closed loop. A broken MAP and and open loop is asking for trouble.

//RF

RS-Chevy-SS

Yeah I know man....But i looked at how much it would be to get the cable shipped and all and it turns out to be 70 and that is outragious

RFmaster

Regulator

You can make a cable yourself minus fancy 12 PIN connector. It takes two transistors couple resistors - probably about $8 to 10 total. Take a look at it. Yes, I know it will be flimsy and DIY looking. Find a HAM friend and most likely he would have all parts handy in a junk box.

//RF