Hi i need help. Please!


My name is Scott Stevens


i have a 1995 SC1 with a SC2 motor in it. When the engine is cold it runs great for about 3 minutes. once my engine starts getting warm I loose power. A lot a power. I have to floor it to accelerate and its a little jerky around 2000-3000 rpm. It seems like my engine is working really hard. What can I do to fix this? I need it to get me through the winter.


I put innew spark plugs and an ECTS. Did not help.

Oh one more thing. When I give it gas my rpm's jump for half a second and then it flattens out. My rpms don't go up.

is the catalytic convertor original? perhaps have that checked

don't go after abused cat converters, the above post may have a point. try to check new </span>catalytic converters, that should do the trick.</span>

You might want to pull the EGR for inspection. It could be clogged with oil and carbon

Thanks for the info I will get the cat converter checked. After unbolting the EGR where do I look for the oil and carbon?

Look at the bottom of the EGR where it bolts to the block, There are air bypass ports that aregoing to be full of crud. Scrape out the carbon and check the valve seat by putting a lip lock on it and blowing into the port. Manually open and close the valve to check if your getting a good seal. If your EGR is fouled up, you may also want to clean out the air mass meter (throttle body)and intake manifold. Look on the manifold side of the throttle plate for oil and dust build up.Use a shop vac with a small hose attached to suck out all of oil sludge in the intake manifold. Finish cleaning manifold with solvents and rags. My 95 has 210k on it and it runs like a top.Edited by: stevestar99

It is not the catalytic converter. I looked at my EGR and it had some build up. I cleaned it off. The valve closes properly. As for the intake manifold it is bad. The throttle body is greasy. I am cleaning the sludge out now. Hopefully it works.


How did I get the sludge buildup in my intake?


Thanks for the help I appreciate it.

I finished cleaning. It runs better. It ran great for a few minutes. Its still jerks when I accelerate and is a little slow.


Any other suggestions?


Thanks


Scott

Did you clean the vacuum ports on the throttle body realgood ? Also the ECTS can effect performance, change it if you haven't. Check the sensor connectors for corrosion. All of the oil crud is coming from the vent hosethatis connectedfrom the head to the intake manifold.

Put some new plugs in. They maybe fouled from all of the sludge that's been running through the engine

You stated that it's a problem when it's hot. How hot? If your having a problem when it's over the 1/2 on the temp gauge, you can PM me for some modifications to keep the coolant temp under 1/2

I have the same problem. I have not recieved one reply and have given some useful help for others. My SL-2 does the exact thing. My first guess was the Cat Conv but the mechanic says no. I indicated that the knock sensor was replaced which makes absolute sense. Since the engine has electronic spark advance, it relies on the "knocking" sound to indicate the need to retard the spark timing. I personally believe this fixed the problem for one day and then the thing went out again. Anyway the mechanic states that the diagnostic indicated the MAF sensor was bad. This change affected no change and was a waste of money. New plugs did not help. The engine never overheats. The EGR is clean. Please let me know if you get it figured out!!

Did you pull the throttle body and take a look at the intake manifold?

Ok guys. Its been a little while but I have learned something new about my problem. It has nothing to do with being hot or cold. I was driving it home from school and I turned the car off at a red light. I started it and it drove great for a few minutes and went back to running like crap. It is really jerky between 2 and 3 thousand rpms. It bogs down sometimes in that rpm range.


I replaced my ECTS andspark plugs. I cleaned my throttle and intake I got some peppyness back but it still jerks.


Thanks for the info.


Scott

I was wrong it still drives better cold.


Please Help.

If your running OK at 1/4 on the temp gauge you can install a adjustable fan switch to keep your temp low. They're on ebay under pre-96 adjustable fan switch. It doesn't solve the under lying problem, but it's a way to get a round a temp problem

Wait a minute, if you've got a 96 engine in a 95 that's your problem. The temp sensor electronics for fuel mixture are different, All of the electronic wouldhave to be 96 including the PCM. The 95 has a separate temp gauge sensor and the 96 only has the ECTS which also controls the temp gauge. If the temp gauge has been spliced into the ECTS on the 95 electronics package it's going to run like crap. Cut loose the temp gauge if it's spliced in, see what happens.


Question; Do you have the single wire temp sensor and the two wire ECTS.Edited by: stevestar99

Scott, it sounds like you are dangerously close to locating the problem. Please keep me posted if you get to the bottom of it. I am at my wits end and am tired of giving a mechanic money for parts changing. I am pretty darn good in the shop myself and am frustrated with these computer problems keeping me from my cars running right. I can overhaul it and rebuild it, dissassemble it and put it back together but I can't troubleshoot properly because of the data inputs supplied by the ancillary devices like the MAF, ECG, water temp sensor data, etc, ect..

Scott, I just flashed on something out of the past. I use to have a 280zx that had a similar problem when you would try to accelerate it would bog down, loose power and would die if I didn't back off on the gas. It was the air mass meter, known on the Saturn as the throttle body. The throttle bodyis a variable resister.The air re-stricter plate is the wiper arm on thevariable resister. If you have a bad spot on the resister, the wiper arm loose the signal when it hits the bad spot and regains the signal once it pass it. Is the problem more related to the throttle position vs rpm?When you go up a steep hill, press way down on the gas peddle and see if it will run though the 2k-3k range ok. Like wise, going down a hill try to place the throttle in the same position as it would be on flat ground in respect to 2k-3k range. You should be running at a higher rpm down hill, with the flat ground 2k-3k position. If it's clunking out at a high rpm down hill, then thisindicates throttlebody could be a fault. Put the car in park andopen and close the TB and see if crapping out under no load in one particular spot.If you think you've got a TB problem, you can attach a ohm meter to the wiper arm lead of the TB and ground. Open and close the TB. You should have a linear sweep. For example if the TB is closed and your reading 0 ohms and wide open it reads 300 ohm. half should be at 150, 1/4 should be 75 and so on. If you sweep all the way through open and closed, and at some point it jumps from a normal reading of 45 ohms up to infinity and back down to 50 ohms as you sweep, then theinfinity reading is going to be the bad spot on the TB. I have no idea if this has anything to do with your problem, but is something to check if you're grasping at straws. This is a common failure with the old air mass meters. I don't know if Saturn's TB is fail proof.

Here's an update on the TB check out. The TB has a potentiometer that's attached to the air restricter plate. It has three leads. One is ground, one is B+ (a regulated voltage) and third lead is the wiper arm. If you unplug the jack and look that the harnessplug with the clip in the up position. The ground is top left pin, B+ is the right top pin, and the wiper arm is the bottom single pin.


B+/\/\/\/\/\/\/\/\/\/\/\/\ ground 5wiper arm

Steve,


Now that is some good information! I am suggesting you for teacher of the year. Honestly, I think you have nailed my problem and I cannot wait to check the linearity of my throttle body restrictor plate wiper arm. Steve, let me know what you find out too. I won't get at my Saturn until my wife gets off shift Sunday at 7:00. The lag is now well defined and an explanation exists. In addition, a troubleshooting methodology has been identified.

Steve,


I checked the potentiometer on the restrictor plate. It is a 1/4 turn pot. The outcome is exactly what you theroized; on the low end-what would be a high idle- the pot what intermittently steady at best. In fact, the pot would not post a reading every time for the first 1/32 turn or so. Further into the resistor, it was very hard to hold a steady resistance. Up into fast idle and then higher speeds the pot was easy to hold any value of resistance. I checked this numerous times with the meter aligator clipped to the plug prongs and the meter situated where I could read it from inside the car so all readings were from foot adjustment rather than trying to hold steady with my hand. I am convinced that the situation would be exacerbated at higher temps. The engine was cold for this test. I will replace the pot and reply. Thanks again for the excellent insight.

Ken, sounds good but you might want to check one more thing before you shell out any more money on parts that you don't need. On the B+ side of the pot, make sure that the voltage is not bouncing up and down. I'm not sure if Saturn does it this way but if the B+ sidevoltage where controlled by the other sensors (ECTS, MAP,etc) it would be a way of changing the fuel mixture. All of the numbersthat I'm giving are just made up for an example, this may or may not be true. You need to check it out for yourself. Let us saywhen the engine is cold the B+ is 9.25v and the wiper is reading 2.56v at certain position. As the engine warms up the B+ is dropping. Now lets say at 1/4 on the temp gauge the B+ is at 8.75v, the wiper arm voltage would drop to 2.40v at the same position. This would effectively give you less gas for the same amount of air. Again I'm not surethat they're doing it this way. The wiper voltage may being adjusted on the wiper side. The PCM is a mystery as to how each sensor is tied into each other to give the finale injector drive voltage.


I'm working on cooling fan "on" control voltages. Here's my method of plotting the control voltages. With the engine cold, write down what each sensor voltage is reading. Do it again at 1/8, 1/4, 3/8 and 1/2. The two wire sensors are thermistors (ECTS) Theydrop their resistance as they get warmer. The one wire sensors (O2) are also thermistors that use chassis ground as one end of the thermistor. Here's where it can get screwy. The PCM has an eprom that has all of the sensor voltages programed in. The epromtells the PCM, is sensor should be reading this when this other sensor is reading that and ifit's not, make up a default reading. It's a house of cards, pull this card out nothing happens. Pull that card out and the whole thing collapses. What you need to do is go down toRadio Shack and pick-up some pots to substitute them into the circuit where the sensors are. 1k and 10k would give you a good range of resistances.

Your words underline the reason I hate the auto underworld. This underworld controls the good information. Every voltage at the PCM should be known for a given set of conditions. This way, someone such as myself would not have to go fishing for answers by reproducing the actual running scenario. The problem with replicating voltage levels with radioshack parts is twofold: One, it's just as likely I will get a bad new part and not be able to hold the value of voltage precicely at the inputs; and two, I have no assurance the voltage levels I produce would be required at the PCM. I am happy to know that the pot is not linear in the most used region. I am not above installing a psuedo resistor in parallel with the existing one in order to increase resolution just to see, but likely I will just install a new trimmer and watch. At least I will be replacing a known bad part even if it's not the final solution.

Yes, I agree with you. Just get it fixed. But if the time comes that it is necessary to do further trouble shooting, the sub pots come in handy to hold sensor voltages at a constant level. If you where to take a resistance reading of the ECTS cold (282 ohms), dial up 282 on the 1k pot and sub it into the circuit, you can hold the PCM temp sensor stable to check other signal voltage changes. I'm an electronics tech by profession and sometimes it becomes necessary to break down a system into sub-systems. Normally the sub-systems will have feed-back loops to other sub-systems. One component can appear to to bad when it's an other's feed back causing theproblem. One time I had a Jagthat had a problem with the delayed entry system.After 3 days of having all of the under dash electronic pulled out, I noticedthat the right rear stereo speaker wasn't working.I pulled the back seat out to find the ground on the speaker was shorting to chassis ground. I fixed the spk problem and that took care of the security systems failure.Um, now that makes sense, a bad spk ground will cause the delayed entry not to activate.I'm guessing that the DE cpu was doing a sweep of all protected devices and not getting a green light to activate. The reason it's a guess is because manufactures won't release detailed info on their electronic packages. Your lucky to get a block diagram. At one time I was able to get the firmware for certain devices that I was making programed changes to. Now when I call a manufacture for firmware, the response is "when hell freezes over you'll get it"

sounds like one of a few things. plugged exhause but it shouldn't matter too much hot or cold. coil packs are bad for corroding (white powder on the teminals under the plug boot)and plug wires are bad for causing a major lack of power and a bucking feel under acceleration hot. Also the egr valves can give a rough run at cruse but normally not to the point where the car is undrivable.keep me posted

Well, enough time has passed to report that the throttle position sensor was indeed the problem in my '98 sl-2. The problem was that there was about a 75% decrease in power at low speeds (around town, etc.) but highway travel was normal. The TPS was not sending the appropriate voltage levels to the computer at low speeds which was attributed to TPS failure at the low end of the potentiometer which is also the most used area.

Its been a while but I finally found out that my computer was reading my ECTS wrong. I tried everything that was suggested but it didn't help. So i took it to a mechanic and they found it was my computer. PCM. I replaced it and it works great. Thanks for the info everyone. I appreciate it.


~Scott

are you still using the original computer? if so put in a dohc computer