Engine idle fluctuates

ANSWER : This may need to have the throttle stop screw adjusted. The throttle stop screw’s primary function is to prevent the throttle blade from closing too far and getting wedged/stuck in the throttle bore. However, it serves as a secondary function to adjust the minimum air setting. The “minimum air setting” is what is used to describe the amount of air that is allowed to enter the engine thru a “closed” throttle. Because the throttle valve cannot be allowed to completely close (because this would result in it getting wedged/stuck closed in the throttle bore), some air will always be allowed to enter the engine around the throttle valve. On a 100% factory stock engine, you should never need to adjust the throttle stop screw. But there are times when the adjustment of this screw is necessary. One example of this is when the engine is modified, or a different throttle body is being used than what originally came with the engine. Larger displacement engines require more air to maintain a set idle speed. Aftermarket camshafts with lots of duration or lots of overlap tend to lower the amount of vacuum an engine can generate at idle. Lower vacuum levels translate to less pressure differential between the intake manifold and outside (ambient) air. This means there isn’t as much pressure difference to force air into the engine around the throttle blade or thru the IAC passage at idle. Either the IAC needs to open up or the throttle blade must be opened more to allow more air to enter the engine. Engines that have higher compression or are new/rebuilt can have higher internal loads/friction which can also result in a drop of idle vacuum levels. In short, any condition that increases load on the engine will result in the vacuum level to drop at idle, which will require the IAC or throttle blade to be opened up to compensate.

ANSWER : Hi there. This can be caused by the issues that you mentioned or a number of other things. You need to make sure all of the connectors are making good contact. I would then need to know what codes are in the computer to know if this is a circuit issue or not. Most of the time, it is not the circuit but instead a vacuum leak.

If there is a vacuum leak, then the vehicle will act like this and the computer cannot control the idle. Most of the time it is a bad hose or an EGR valve that is stuck open. That is the most common cause for this. I typically remove the EGR to check it to feel the diaphragm on the bottom of it to see if it is moving correctly. If you need to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair your car’s idling issue.

ANSWER : Hi there. The issue seems to be a vacuum leak on the engine. Get a stethoscope that is made for automotive vehicles and listen for a hissing noise around the intake gasket or the intake hosing to the throttle valve. If there is a hissing noise, then the gasket or hoses are in need of replacement. A vacuum leak on the engine will cause the idle to hunt when operating. If you need further assistance with your engine idle hunting, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hello. I would start by scanning the vehicle for codes and checking to see if all of the sensors are reading correctly. If everything looks good then chances are it needs a new computer. I have seen the computers fail on these vehicles over and over again causing the ignition circuits to not work correctly which causes the vehicle to run just like this. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to you to [diagnose why the vehicle is running like this] https://www.yourmechanic.com/services/car-idle-is-rough-inspection

ANSWER : Anything is possible with enough engineering. The changes you are looking at would take major structural changes and would definitely not be an easy job. You could possibly consult a manufacturing engineer to get more details on how this could actually be carried out and whether it would be feasible.

ANSWER : You could try cleaning the throttle body and idle control valve. If the engine has a vacuum leak, then fix the leak. An idle of around 900 RPMs is about normal for most manual transmission vehicles and you may have other problems causing the engine to stall.

If you need help then have a qualified mechanic run a diagnostic inspection and recommend the best path to repair.

ANSWER : An engine computer cannot control, or affect, "basic" engine mechanical compression, that is the level of cylinder compression measured in a static test. Even in the complete absence of any engine computer, the basic specified compression of an engine will exist. If the engine doesn’t have the minimum specified compression, then the engine is mechanically broken. If the timing belt on the engine is in the correct position, the SOLE determinants of engine compression, during the typical static test, are: 1) the condition of the cylinder walls and the piston rings; 2) the condition of the engine valves and valve train; and 3) the condition of the head gasket. Consequently, if the engine has no, or little, compression during a test with the throttle held open, there is a mechanical problem with the engine, not an electrical problem. I would first check to be sure the timing belt has not slipped; that fault alone can ruin compression. If the timing belt has not slipped, and you desire a run down of your options to get this resolved, please request a rough engine operation diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.

ANSWER : Hi…thank you for your questions. If required in the application, a portable engine support bar is used to support an engine during mount replacement. The support bar has lifting capability as well so that the mount can be unloaded and removed. If a particular repair application requires a "crane" (complete engine removal for instance), such are portable these days in any event. With regard to the exhaust system repair, mechanics use ramps to gain access. Six ton portable jack stands will safely support a car two feet into the air which provides more than enough access to repair or replace any exhaust system component. If you desire replacement of the mounts, please refer to YourMechanic’s motor mount replacement service page. For exhaust leaks, please use the exhaust system inspection/repair page page. Once on each of those service pages, if you click on "Get a Quote" and enter your vehicle information (year, make, model) you can obtain cost info and schedule the service. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.